diff --git a/python/core/auto_generated/qgsaction.sip.in b/python/core/auto_generated/qgsaction.sip.in
index 71ae7de3669d..29a4eb531db0 100644
--- a/python/core/auto_generated/qgsaction.sip.in
+++ b/python/core/auto_generated/qgsaction.sip.in
@@ -27,6 +27,8 @@ Utility class that encapsulates an action based on vector attributes.
       Windows,
       Unix,
       OpenUrl,
+      SubmitUrlEncoded,
+      SubmitUrlMultipart,
     };
 
     QgsAction();
diff --git a/resources/function_help/json/url_encode b/resources/function_help/json/url_encode
new file mode 100644
index 000000000000..0cd91eab1aac
--- /dev/null
+++ b/resources/function_help/json/url_encode
@@ -0,0 +1,18 @@
+{
+  "name": "url_encode",
+  "type": "function",
+  "groups": ["Maps"],
+  "description": "Returns an URL encoded string from a map. Transforms all characters in their properly-encoded form producing a fully-compliant query string.<br>Note that the plus sign '+' is not converted.",
+  "arguments": [
+    {
+      "arg": "map",
+      "description": "a map."
+    }
+  ],
+  "examples": [
+    {
+      "expression": "url_encode(map('a&+b', 'a and plus b', 'a=b', 'a equals b'))",
+      "returns": "'a%26+b=a%20and%20plus%20b&a%3Db=a%20equals%20b'"
+    }
+  ]
+}
diff --git a/src/core/expression/qgsexpressionfunction.cpp b/src/core/expression/qgsexpressionfunction.cpp
index 530373ee388c..52f43be2d13c 100644
--- a/src/core/expression/qgsexpressionfunction.cpp
+++ b/src/core/expression/qgsexpressionfunction.cpp
@@ -69,6 +69,7 @@
 #include <QCryptographicHash>
 #include <QRegularExpression>
 #include <QUuid>
+#include <QUrlQuery>
 
 typedef QList<QgsExpressionFunction *> ExpressionFunctionList;
 
@@ -6536,6 +6537,17 @@ static QVariant fcnToBase64( const QVariantList &values, const QgsExpressionCont
   return QVariant( QString( input.toBase64() ) );
 }
 
+static QVariant fcnToFormUrlEncode( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  const QVariantMap map = QgsExpressionUtils::getMapValue( values.at( 0 ), parent );
+  QUrlQuery query;
+  for ( auto it = map.cbegin(); it != map.cend(); it++ )
+  {
+    query.addQueryItem( it.key(), it.value().toString() );
+  }
+  return query.toString( QUrl::ComponentFormattingOption::FullyEncoded );
+}
+
 static QVariant fcnFromBase64( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
 {
   const QString value = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
@@ -8020,6 +8032,8 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
         << new QgsStaticExpressionFunction( QStringLiteral( "map_prefix_keys" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "map" ) )
                                             << QgsExpressionFunction::Parameter( QStringLiteral( "prefix" ) ),
                                             fcnMapPrefixKeys, QStringLiteral( "Maps" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "url_encode" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "map" ) ),
+                                            fcnToFormUrlEncode, QStringLiteral( "Maps" ) )
 
         ;
 
diff --git a/src/core/network/qgsnetworkaccessmanager.cpp b/src/core/network/qgsnetworkaccessmanager.cpp
index 01c67c08ec65..651c2002af97 100644
--- a/src/core/network/qgsnetworkaccessmanager.cpp
+++ b/src/core/network/qgsnetworkaccessmanager.cpp
@@ -353,6 +353,11 @@ QNetworkReply *QgsNetworkAccessManager::createRequest( QNetworkAccessManager::Op
   {
     content = buffer->buffer();
   }
+  else if ( outgoingData )
+  {
+    content = outgoingData->readAll();
+    outgoingData->seek( 0 );
+  }
 
   emit requestAboutToBeCreated( QgsNetworkRequestParameters( op, req, requestId, content ) );
   Q_NOWARN_DEPRECATED_PUSH
diff --git a/src/core/qgsaction.cpp b/src/core/qgsaction.cpp
index 261d3ba5340c..60783ea2498a 100644
--- a/src/core/qgsaction.cpp
+++ b/src/core/qgsaction.cpp
@@ -19,6 +19,13 @@
 #include <QDesktopServices>
 #include <QFileInfo>
 #include <QUrl>
+#include <QUrlQuery>
+#include <QDir>
+#include <QTemporaryDir>
+#include <QNetworkRequest>
+#include <QJsonDocument>
+#include <QHttpMultiPart>
+#include <QMimeDatabase>
 
 #include "qgspythonrunner.h"
 #include "qgsrunprocess.h"
@@ -26,12 +33,18 @@
 #include "qgsvectorlayer.h"
 #include "qgslogger.h"
 #include "qgsexpressioncontextutils.h"
+#include "qgswebview.h"
+#include "qgsnetworkaccessmanager.h"
+#include "qgsmessagelog.h"
+
 
 bool QgsAction::runable() const
 {
   return mType == Generic ||
          mType == GenericPython ||
          mType == OpenUrl ||
+         mType == SubmitUrlEncoded ||
+         mType == SubmitUrlMultipart ||
 #if defined(Q_OS_WIN)
          mType == Windows
 #elif defined(Q_OS_MAC)
@@ -52,6 +65,173 @@ void QgsAction::run( QgsVectorLayer *layer, const QgsFeature &feature, const Qgs
   run( actionContext );
 }
 
+void QgsAction::handleFormSubmitAction( const QString &expandedAction ) const
+{
+
+  QUrl url{ expandedAction };
+
+  // Encode '+' (fully encoded doesn't encode it)
+  const QString payload { url.query( QUrl::ComponentFormattingOption::FullyEncoded ).replace( QChar( '+' ), QStringLiteral( "%2B" ) ) };
+
+  // Remove query string from URL
+  const QUrlQuery queryString { url.query( ) };
+  url.setQuery( QString( ) );
+
+  QNetworkRequest req { url };
+
+  // Specific code for testing, produces an invalid POST but we can still listen to
+  // signals and examine the request
+  if ( url.toString().contains( QLatin1String( "fake_qgis_http_endpoint" ) ) )
+  {
+    req.setUrl( QStringLiteral( "file://%1" ).arg( url.path() ) );
+  }
+
+  QNetworkReply *reply = nullptr;
+
+  if ( mType != QgsAction::SubmitUrlMultipart )
+  {
+    QString contentType { QStringLiteral( "application/x-www-form-urlencoded" ) };
+    // check for json
+    QJsonParseError jsonError;
+    QJsonDocument::fromJson( payload.toUtf8(), &jsonError );
+    if ( jsonError.error == QJsonParseError::ParseError::NoError )
+    {
+      contentType = QStringLiteral( "application/json" );
+    }
+    req.setHeader( QNetworkRequest::KnownHeaders::ContentTypeHeader, contentType );
+    reply = QgsNetworkAccessManager::instance()->post( req, payload.toUtf8() );
+  }
+  // for multipart create parts and headers
+  else
+  {
+    QHttpMultiPart *multiPart = new QHttpMultiPart( QHttpMultiPart::FormDataType );
+    const QList<QPair<QString, QString>> queryItems { queryString.queryItems( QUrl::ComponentFormattingOption::FullyDecoded ) };
+    for ( const QPair<QString, QString> &queryItem : std::as_const( queryItems ) )
+    {
+      QHttpPart part;
+      part.setHeader( QNetworkRequest::ContentDispositionHeader,
+                      QStringLiteral( "form-data; name=\"%1\"" )
+                      .arg( QString( queryItem.first ).replace( '"', QStringLiteral( R"(\")" ) ) ) );
+      part.setBody( queryItem.second.toUtf8() );
+      multiPart->append( part );
+    }
+    reply = QgsNetworkAccessManager::instance()->post( req, multiPart );
+    multiPart->setParent( reply );
+  }
+
+  QObject::connect( reply, &QNetworkReply::finished, reply, [ reply ]
+  {
+    if ( reply->error() == QNetworkReply::NoError )
+    {
+
+      if ( reply->attribute( QNetworkRequest::RedirectionTargetAttribute ).isNull() )
+      {
+
+        const QByteArray replyData = reply->readAll();
+
+        QString filename { "download.bin" };
+        if ( const std::string header = reply->header( QNetworkRequest::KnownHeaders::ContentDispositionHeader ).toString().toStdString(); ! header.empty() )
+        {
+
+          std::string ascii;
+          const std::string q1 { R"(filename=")" };
+          if ( const unsigned long pos = header.find( q1 ); pos != std::string::npos )
+          {
+            const unsigned long len = pos + q1.size();
+
+            const std::string q2 { R"(")" };
+            if ( unsigned long pos = header.find( q2, len ); pos != std::string::npos )
+            {
+              bool escaped = false;
+              while ( pos != std::string::npos && header[pos - 1] == '\\' )
+              {
+                pos = header.find( q2, pos + 1 );
+                escaped = true;
+              }
+              ascii = header.substr( len, pos - len );
+              if ( escaped )
+              {
+                std::string cleaned;
+                for ( size_t i = 0; i < ascii.size(); ++i )
+                {
+                  if ( ascii[i] == '\\' )
+                  {
+                    if ( i > 0 && ascii[i - 1] == '\\' )
+                    {
+                      cleaned.push_back( ascii[i] );
+                    }
+                  }
+                  else
+                  {
+                    cleaned.push_back( ascii[i] );
+                  }
+                }
+                ascii = cleaned;
+              }
+            }
+          }
+
+          std::string utf8;
+
+          const std::string u { R"(UTF-8'')" };
+          if ( const unsigned long pos = header.find( u ); pos != std::string::npos )
+          {
+            utf8 = header.substr( pos + u.size() );
+          }
+
+          // Prefer ascii over utf8
+          if ( ascii.empty() )
+          {
+            if ( ! utf8.empty( ) )
+            {
+              filename = QString::fromStdString( utf8 );
+            }
+          }
+          else
+          {
+            filename = QString::fromStdString( ascii );
+          }
+        }
+        else if ( !reply->header( QNetworkRequest::KnownHeaders::ContentTypeHeader ).isNull() )
+        {
+          QString contentTypeHeader { reply->header( QNetworkRequest::KnownHeaders::ContentTypeHeader ).toString() };
+          // Strip charset if any
+          if ( contentTypeHeader.contains( ';' ) )
+          {
+            contentTypeHeader = contentTypeHeader.left( contentTypeHeader.indexOf( ';' ) );
+          }
+
+          QMimeType mimeType { QMimeDatabase().mimeTypeForName( contentTypeHeader ) };
+          if ( mimeType.isValid() )
+          {
+            filename = QStringLiteral( "download.%1" ).arg( mimeType.preferredSuffix() );
+          }
+        }
+
+        QTemporaryDir tempDir;
+        tempDir.setAutoRemove( false );
+        tempDir.path();
+        const QString tempFilePath{ tempDir.path() + QDir::separator() + filename };
+        QFile tempFile{ tempFilePath };
+        tempFile.open( QIODevice::WriteOnly );
+        tempFile.write( replyData );
+        tempFile.close();
+        QDesktopServices::openUrl( QUrl::fromLocalFile( tempFilePath ) );
+      }
+      else
+      {
+        QgsMessageLog::logMessage( QObject::tr( "Redirect is not supported!" ), QStringLiteral( "Form Submit Action" ), Qgis::MessageLevel::Critical );
+      }
+    }
+    else
+    {
+      QgsMessageLog::logMessage( reply->errorString(), QStringLiteral( "Form Submit Action" ), Qgis::MessageLevel::Critical );
+    }
+    reply->deleteLater();
+  } );
+
+}
+
 void QgsAction::run( const QgsExpressionContext &expressionContext ) const
 {
   if ( !isValid() )
@@ -74,6 +254,11 @@ void QgsAction::run( const QgsExpressionContext &expressionContext ) const
     else
       QDesktopServices::openUrl( QUrl( expandedAction, QUrl::TolerantMode ) );
   }
+  else if ( mType == QgsAction::SubmitUrlEncoded || mType == QgsAction::SubmitUrlMultipart )
+  {
+    handleFormSubmitAction( expandedAction );
+
+  }
   else if ( mType == QgsAction::GenericPython )
   {
     // TODO: capture output from QgsPythonRunner (like QgsRunProcess does)
@@ -200,6 +385,16 @@ QString QgsAction::html() const
       typeText = QObject::tr( "Open URL" );
       break;
     }
+    case SubmitUrlEncoded:
+    {
+      typeText = QObject::tr( "Submit URL (urlencoded or JSON)" );
+      break;
+    }
+    case SubmitUrlMultipart:
+    {
+      typeText = QObject::tr( "Submit URL (multipart)" );
+      break;
+    }
   }
   return { QObject::tr( R"html(
 <h2>Action Details</h2>
diff --git a/src/core/qgsaction.h b/src/core/qgsaction.h
index 95e011bdd175..e99fadbad5ce 100644
--- a/src/core/qgsaction.h
+++ b/src/core/qgsaction.h
@@ -42,6 +42,8 @@ class CORE_EXPORT QgsAction
       Windows,
       Unix,
       OpenUrl,
+      SubmitUrlEncoded, //!< POST data to an URL, using "application/x-www-form-urlencoded" or "application/json" if the body is valid JSON \since QGIS 3.24
+      SubmitUrlMultipart, //!< POST data to an URL using "multipart/form-data"  \since QGIS 3.24
     };
 
     /**
@@ -255,6 +257,8 @@ class CORE_EXPORT QgsAction
     QString html( ) const;
 
   private:
+
+    void handleFormSubmitAction( const QString &expandedAction ) const;
     ActionType mType = Generic;
     QString mDescription;
     QString mShortTitle;
diff --git a/src/core/qgsactionmanager.cpp b/src/core/qgsactionmanager.cpp
index bad9fba15519..edef8fd12a37 100644
--- a/src/core/qgsactionmanager.cpp
+++ b/src/core/qgsactionmanager.cpp
@@ -38,11 +38,9 @@
 #include <QSettings>
 #include <QDesktopServices>
 #include <QUrl>
-#include <QDir>
 #include <QFileInfo>
 #include <QRegularExpression>
 
-
 QUuid QgsActionManager::addAction( QgsAction::ActionType type, const QString &name, const QString &command, bool capture )
 {
   QgsAction action( type, name, command, capture );
@@ -189,24 +187,34 @@ QList<QgsAction> QgsActionManager::actions( const QString &actionScope ) const
 
 void QgsActionManager::runAction( const QgsAction &action )
 {
-  if ( action.type() == QgsAction::OpenUrl )
-  {
-    QFileInfo finfo( action.command() );
-    if ( finfo.exists() && finfo.isFile() )
-      QDesktopServices::openUrl( QUrl::fromLocalFile( action.command() ) );
-    else
-      QDesktopServices::openUrl( QUrl( action.command(), QUrl::TolerantMode ) );
-  }
-  else if ( action.type() == QgsAction::GenericPython )
-  {
-    // TODO: capture output from QgsPythonRunner (like QgsRunProcess does)
-    QgsPythonRunner::run( action.command() );
-  }
-  else
+  switch ( action.type() )
   {
-    // The QgsRunProcess instance created by this static function
-    // deletes itself when no longer needed.
-    QgsRunProcess::create( action.command(), action.capture() );
+    case QgsAction::OpenUrl:
+    {
+      QFileInfo finfo( action.command() );
+      if ( finfo.exists() && finfo.isFile() )
+        QDesktopServices::openUrl( QUrl::fromLocalFile( action.command() ) );
+      else
+        QDesktopServices::openUrl( QUrl( action.command(), QUrl::TolerantMode ) );
+      break;
+    }
+    case QgsAction::GenericPython:
+    case QgsAction::SubmitUrlEncoded:
+    case QgsAction::SubmitUrlMultipart:
+    {
+      action.run( QgsExpressionContext() );
+      break;
+    }
+    case QgsAction::Generic:
+    case QgsAction::Mac:
+    case QgsAction::Unix:
+    case QgsAction::Windows:
+    {
+      // The QgsRunProcess instance created by this static function
+      // deletes itself when no longer needed.
+      QgsRunProcess::create( action.command(), action.capture() );
+      break;
+    }
   }
 }
 
diff --git a/src/gui/vector/qgsattributeactiondialog.cpp b/src/gui/vector/qgsattributeactiondialog.cpp
index 7b911550ae8d..2a101cdb4db9 100644
--- a/src/gui/vector/qgsattributeactiondialog.cpp
+++ b/src/gui/vector/qgsattributeactiondialog.cpp
@@ -256,6 +256,10 @@ QString QgsAttributeActionDialog::textForType( QgsAction::ActionType type )
       return tr( "Unix" );
     case QgsAction::OpenUrl:
       return tr( "Open URL" );
+    case QgsAction::SubmitUrlEncoded:
+      return tr( "Submit URL (urlencoded or JSON)" );
+    case QgsAction::SubmitUrlMultipart:
+      return tr( "Submit URL (multipart)" );
   }
   return QString();
 }
diff --git a/src/ui/qgsattributeactionpropertiesdialogbase.ui b/src/ui/qgsattributeactionpropertiesdialogbase.ui
index c0556056f5a2..ecca0e177017 100644
--- a/src/ui/qgsattributeactionpropertiesdialogbase.ui
+++ b/src/ui/qgsattributeactionpropertiesdialogbase.ui
@@ -234,7 +234,17 @@
      </item>
      <item>
       <property name="text">
-       <string>Open</string>
+       <string>Open URL</string>
+      </property>
+     </item>
+     <item>
+      <property name="text">
+       <string>Submit URL (urlencoded or JSON)</string>
+      </property>
+     </item>
+     <item>
+      <property name="text">
+       <string>Submit URL (multipart)</string>
       </property>
      </item>
     </widget>
@@ -325,32 +335,6 @@
  <resources>
   <include location="../../images/images.qrc"/>
   <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
-  <include location="../../images/images.qrc"/>
  </resources>
  <connections>
   <connection>
diff --git a/tests/src/core/testqgsexpression.cpp b/tests/src/core/testqgsexpression.cpp
index 45a3228a00b5..5bf266064f9c 100644
--- a/tests/src/core/testqgsexpression.cpp
+++ b/tests/src/core/testqgsexpression.cpp
@@ -1980,6 +1980,11 @@ class TestQgsExpression: public QObject
       QTest::newRow( "exif bad file path" ) << QStringLiteral( "exif('bad path','Exif.Image.DateTime')" ) << false << QVariant();
       QTest::newRow( "exif_geotag" ) << QStringLiteral( "geom_to_wkt(exif_geotag('%1photos/0997.JPG'))" ).arg( testDataDir ) << false << QVariant( "PointZ (149.27516667 -37.2305 422.19101124)" );
       QTest::newRow( "exif_geotag bad file path" ) << QStringLiteral( "geom_to_wkt(exif_geotag('bad path'))" ).arg( testDataDir ) << false << QVariant( "Point EMPTY" );
+
+      // Form encoding tests
+      QTest::newRow( "url_encode" ) << QStringLiteral( "url_encode(map())" ).arg( testDataDir ) << false << QVariant( "" );
+      QTest::newRow( "url_encode" ) << QStringLiteral( "url_encode(map('a b', 'a b', 'c &% d', 'c &% d'))" ).arg( testDataDir ) << false << QVariant( "a%20b=a%20b&c%20%26%25%20d=c%20%26%25%20d" );
+      QTest::newRow( "url_encode" ) << QStringLiteral( "url_encode(map('a&+b', 'a and plus b', 'a=b', 'a equals b'))" ).arg( testDataDir ) << false << QVariant( "a%26+b=a%20and%20plus%20b&a%3Db=a%20equals%20b" );
     }
 
     void run_evaluation_test( QgsExpression &exp, bool evalError, QVariant &expected )
diff --git a/tests/src/python/CMakeLists.txt b/tests/src/python/CMakeLists.txt
index eaae0775623e..de1615a17314 100644
--- a/tests/src/python/CMakeLists.txt
+++ b/tests/src/python/CMakeLists.txt
@@ -13,6 +13,7 @@ ADD_PYTHON_TEST(PyCoreAdditions test_core_additions.py)
 ADD_PYTHON_TEST(PyPythonRepr test_python_repr.py)
 ADD_PYTHON_TEST(PyPythonUtils test_python_utils.py)
 ADD_PYTHON_TEST(PyQgsActionManager test_qgsactionmanager.py)
+ADD_PYTHON_TEST(PyQgsAction test_qgsaction.py)
 ADD_PYTHON_TEST(PyQgsAFSProvider test_provider_afs.py)
 ADD_PYTHON_TEST(PyQgsAggregateMappingWidget test_qgsaggregatemappingwidget.py)
 ADD_PYTHON_TEST(PyQgsAlignmentComboBox test_qgsalignmentcombobox.py)
diff --git a/tests/src/python/test_qgsaction.py b/tests/src/python/test_qgsaction.py
new file mode 100644
index 000000000000..e64bb9ed26fe
--- /dev/null
+++ b/tests/src/python/test_qgsaction.py
@@ -0,0 +1,102 @@
+# -*- coding: utf-8 -*-
+"""QGIS Unit tests for QgsAction.
+
+From build dir, run: ctest -R PyQgsAction -V
+
+.. note:: This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+"""
+__author__ = 'Alessandro Pasotti'
+__date__ = '24/11/2021'
+__copyright__ = 'Copyright 2021, The QGIS Project'
+
+import qgis  # NOQA switch sip api
+
+from qgis.core import (
+    QgsExpressionContext,
+    QgsAction,
+    QgsNetworkAccessManager,
+    QgsNetworkRequestParameters,
+    QgsApplication,
+)
+
+from qgis.PyQt.QtCore import QTemporaryDir
+
+from qgis.testing import start_app, unittest
+
+import os
+import re
+import time
+import platform
+from functools import partial
+
+start_app()
+
+
+class TestQgsAction(unittest.TestCase):
+
+    def setUp(self):
+        self.body = None
+
+    def _req_logger(self, params):
+        self.body = bytes(params.content())
+
+    def test_post_urlencoded_action(self):
+        """Test form www urlencoded"""
+
+        def _req_logger(self, params):
+            self.body = bytes(params.content())
+
+        QgsNetworkAccessManager.instance().requestAboutToBeCreated[QgsNetworkRequestParameters].connect(partial(_req_logger, self))
+
+        temp_dir = QTemporaryDir()
+        temp_path = temp_dir.path()
+        temp_file = os.path.join(temp_path, 'urlencoded.txt')
+
+        action = QgsAction(QgsAction.SubmitUrlEncoded, 'url_encoded', "http://fake_qgis_http_endpoint" + temp_file + r"?[% url_encode(map('a&+b', 'a and plus b', 'a=b', 'a equals b')) %]")
+        ctx = QgsExpressionContext()
+        action.run(ctx)
+
+        while not self.body:
+            QgsApplication.instance().processEvents()
+
+        self.assertEqual(self.body, br"a%26%2Bb=a%20and%20plus%20b&a%3Db=a%20equals%20b")
+
+    def test_post_multipart_action(self):
+        """Test multipart"""
+
+        self.body = None
+
+        def _req_logger(self, params):
+            self.body = bytes(params.content())
+
+        QgsNetworkAccessManager.instance().requestAboutToBeCreated[QgsNetworkRequestParameters].connect(partial(_req_logger, self))
+
+        temp_dir = QTemporaryDir()
+        temp_path = temp_dir.path()
+        temp_file = os.path.join(temp_path, 'multipart.txt')
+
+        action = QgsAction(QgsAction.SubmitUrlMultipart, 'url_encoded', "http://fake_qgis_http_endpoint" + temp_file + r"?[% url_encode(map('a&+b', 'a and plus b', 'a=b', 'a equals b')) %]")
+        ctx = QgsExpressionContext()
+        action.run(ctx)
+
+        while not self.body:
+            QgsApplication.instance().processEvents()
+
+        self.assertEqual(re.sub(r'\.oOo\.[^\r]*', '.oOo.UUID', self.body.decode('utf8')), '\r\n'.join([
+            '--boundary_.oOo.UUID',
+            'Content-Disposition: form-data; name="a&+b"',
+            '',
+            'a and plus b',
+            '--boundary_.oOo.UUID',
+            'Content-Disposition: form-data; name="a=b"',
+            '',
+            'a equals b',
+            '--boundary_.oOo.UUID',
+            '']))
+
+
+if __name__ == '__main__':
+    unittest.main()