@@ -477,6 +477,11 @@ QgsColorRampShader        {#qgis_api_break_3_0_QgsColorRampShader}
 - maximumColorCacheSize() and setMaximumColorCacheSize() were no longer used and are removed.
 - ColorRamp_TYPE enum was renamed to Type, and its value names decapitalized
 
+QgsColorSchemeRegistry        {#qgis_api_break_3_0_QgsColorSchemeRegistry}
+----------------------
+
+- This class is no longer a singleton and instance() has been removed. Instead use QgsApplication::colorSchemeRegistry() to access an application-wide registry.
+
 
 QgsComposerArrow        {#qgis_api_break_3_0_QgsComposerArrow}
 ----------------
@@ -727,6 +732,12 @@ QgsDataItem        {#qgis_api_break_3_0_QgsDataItem}
 - emitBeginInsertItems(), emitEndInsertItems(), emitBeginRemoveItems(), emitEndRemoveItems(), emitDataChanged(), emitStateChanged() have been removed.
 - Favourites was renamed to Favorites
 
+QgsDataItemProviderRegistry        {#qgis_api_break_3_0_QgsDataItemProviderRegistry}
+---------------------------
+
+- This class is no longer a singleton and instance() has been removed. Instead use QgsApplication::dataItemProviderRegistry() to access an application-wide registry.
+
+
 QgsDataProvider        {#qgis_api_break_3_0_QgsDataProvider}
 ---------------
 
@@ -986,6 +997,11 @@ QgsEditorWidgetFactory         {#qgis_api_break_3_0_QgsEditorWidgetFactory}
 - `alignmentFlag` has been removed. Use QgsFieldFormatter::representValue() instead
 - `createCache` has been removed. Use QgsFieldFormatter::representValue() instead
 
+QgsGPSConnectionRegistry        {#qgis_api_break_3_0_QgsGPSConnectionRegistry}
+------------------------
+
+- This class is no longer a singleton and instance() has been removed. Instead use QgsApplication::gpsConnectionRegistry() to access an application-wide registry.
+
 
 QgsGraduatedRenderer        {#qgis_api_break_3_0_QgsGraduatedRenderer}
 --------------------
@@ -1208,6 +1224,12 @@ QgsMarkerSymbolLayer        {#qgis_api_break_3_0_QgsMarkerSymbolLayer}
 - bounds() is now pure virtual and must be implemented in all subclasses.
 
 
+QgsMessageLog        {#qgis_api_break_3_0_QgsMessageLog}
+---------------------------
+
+- This class is no longer a singleton and instance() has been removed. Instead use QgsApplication::messageLog() to access an application-wide log.
+
+
 QgsMimeDataUtils        {#qgis_api_break_3_0_QgsMimeDataUtils}
 ----------------
 
@@ -1258,6 +1280,11 @@ QgsNumericSortTreeWidgetItem        {#qgis_api_break_3_0_QgsNumericSortTreeWidge
 has improved sort capabilities including the ability to set custom sort values for items
 and for forcing certain items to always sort on top.
 
+QgsPaintEffectRegistry        {#qgis_api_break_3_0_QgsPaintEffectRegistry}
+----------------------
+
+- This class is no longer a singleton and instance() has been removed. Instead use QgsApplication::paintEffectRegistry() to access an application-wide registry.
+
 
 QgsPalettedRasterRenderer        {#qgis_api_break_3_0_QgsPalettedRasterRenderer}
 -------------------------
@@ -1300,6 +1327,12 @@ QgsPluginLayer        {#qgis_api_break_3_0_QgsPluginLayer}
 - createMapRenderer(): default implementation (which called plugin's draw() method) has been removed. Plugin layers must implement createMapRenderer().
 
 
+QgsPluginLayerRegistry        {#qgis_api_break_3_0_QgsPluginLayerRegistry}
+----------------------
+
+- This class is no longer a singleton and instance() has been removed. Instead use QgsApplication::pluginLayerRegistry() to access an application-wide registry.
+
+
 QgsPointDisplacementRenderer        {#qgis_api_break_3_0_QgsPointDisplacementRenderer}
 ----------------------------
 
@@ -1405,6 +1438,12 @@ be returned instead of a null pointer if no transformation is required.
 - setCoordinateTransform() now takes a QgsCoordinateTransform reference, not a pointer. An invalid QgsCoordinateTransform should be used instead of a null pointer if no transformation is required.
 
 
+QgsRendererRegistry        {#qgis_api_break_3_0_QgsRendererRegistry}
+----------------------
+
+- This class is no longer a singleton and instance() has been removed. Instead use QgsApplication::rendererRegistry() to access an application-wide registry.
+
+
 QgsRendererWidget        {#qgis_api_break_3_0_QgsRendererWidget}
 -----------------
 
@@ -1486,6 +1525,7 @@ QgsSublayersDialog        {#qgis_api_break_3_0_QgsSublayersDialog}
 QgsSvgCache        {#qgis_api_break_3_0_QgsSvgCache}
 -----------
 
+- This class is no longer a singleton and instance() has been removed. Instead use QgsApplication::svgCache() to access an application-wide cache.
 - containsParamsV2() was removed. Use containsParamsV3() instead.
 
 QgsStyle (renamed from QgsStyleV2)        {#qgis_api_break_3_0_QgsStyle}
@@ -1519,6 +1559,11 @@ the variant which takes QgsSymbolRenderContext instead.
 - evaluateDataDefinedProperty( const QString& property, const QgsFeature* feature ) was removed. Use the variant which takes QgsSymbolRenderContext instead.
 - expression() was removed. Use getDataDefinedProperty or evaluateDataDefinedProperty instead.
 
+QgsSymbolLayerRegistry        {#qgis_api_break_3_0_QgsSymbolLayerRegistry}
+----------------------
+
+- This class is no longer a singleton and instance() has been removed. Instead use QgsApplication::symbolLayerRegistry() to access an application-wide registry.
+
 
 QgsSymbolLayerWidget        {#qgis_api_break_3_0_QgsSymbolLayerWidget}
 --------------------
 
@@ -246,7 +246,7 @@ def calculation_finished(exception, value=None):
 
     task = QgsTask.fromFunction('my task', calculate,
             on_finished=calculation_finished)
-    QgsTaskManager.instance().addTask(task)
+    QgsApplication.taskManager().addTask(task)
 
     """
 
 
@@ -67,9 +67,8 @@ class QgsPaintEffectRegistry
 
   public:
 
-    /** Returns a reference to the singleton instance of the paint effect registry.
-     */
-    static QgsPaintEffectRegistry* instance();
+    QgsPaintEffectRegistry();
+    ~QgsPaintEffectRegistry();
 
     /** Returns the metadata for a specific effect.
      * @param name unique string name for paint effect class
@@ -120,10 +119,6 @@ class QgsPaintEffectRegistry
      */
     static bool isDefaultStack( QgsPaintEffect* effect );
 
-  protected:
-    QgsPaintEffectRegistry();
-    ~QgsPaintEffectRegistry();
-
   private:
     QgsPaintEffectRegistry( const QgsPaintEffectRegistry& rh );
 };
 
@@ -6,7 +6,7 @@ class QgsGPSConnectionRegistry
 #include <qgsgpsconnectionregistry.h>
 %End
   public:
-    static QgsGPSConnectionRegistry* instance();
+    QgsGPSConnectionRegistry();
     ~QgsGPSConnectionRegistry();
 
     /** Inserts a connection into the registry. The connection is owned by the registry class until it is unregistered again*/
@@ -16,9 +16,6 @@ class QgsGPSConnectionRegistry
 
     QList< QgsGPSConnection *> connectionList() const;
 
-  protected:
-    QgsGPSConnectionRegistry();
-
   private:
 
     QgsGPSConnectionRegistry( const QgsGPSConnectionRegistry& rh );
 
@@ -381,6 +381,62 @@ static void qtgui_UpdatePyArgv(PyObject *argvlist, int argc, char **argv)
      */
     static QgsTaskManager* taskManager();
 
+    /**
+     * Returns the application's color scheme registry, used for managing color schemes.
+     * @note added in QGIS 3.0
+     */
+    static QgsColorSchemeRegistry* colorSchemeRegistry();
+
+    /**
+     * Returns the application's paint effect registry, used for managing paint effects.
+     * @note added in QGIS 3.0
+     */
+    static QgsPaintEffectRegistry* paintEffectRegistry();
+
+    /**
+     * Returns the application's renderer registry, used for managing vector layer renderers.
+     * @note added in QGIS 3.0
+     */
+    static QgsRendererRegistry* rendererRegistry();
+
+    /**
+     * Returns the application's data item provider registry, which keeps a list of data item
+     * providers that may add items to the browser tree.
+     * @note added in QGIS 3.0
+     */
+    static QgsDataItemProviderRegistry* dataItemProviderRegistry();
+
+    /**
+     * Returns the application's SVG cache, used for caching SVG images and handling parameter replacement
+     * within SVG files.
+     * @note added in QGIS 3.0
+     */
+    static QgsSvgCache* svgCache();
+
+    /**
+     * Returns the application's symbol layer registry, used for managing symbol layers.
+     * @note added in QGIS 3.0
+     */
+    static QgsSymbolLayerRegistry* symbolLayerRegistry();
+
+    /**
+     * Returns the application's GPS connection registry, used for managing GPS connections.
+     * @note added in QGIS 3.0
+     */
+    static QgsGPSConnectionRegistry* gpsConnectionRegistry();
+
+    /**
+     * Returns the application's plugin layer registry, used for managing plugin layer types.
+     * @note added in QGIS 3.0
+     */
+    static QgsPluginLayerRegistry* pluginLayerRegistry();
+
+    /**
+     * Returns the application's message log.
+     * @note added in QGIS 3.0
+     */
+    static QgsMessageLog* messageLog();
+
 %If(ANDROID)
     //dummy method to workaround sip generation issue issue
     bool x11EventFilter ( XEvent * event );
 
@@ -14,10 +14,6 @@ class QgsColorSchemeRegistry
 %End
   public:
 
-    /** Returns the global instance pointer, creating the object on the first call.
-     */
-    static QgsColorSchemeRegistry * instance();
-
     /** Constructor for an empty color scheme registry
      */
     QgsColorSchemeRegistry();
 
@@ -11,8 +11,7 @@ class QgsDataItemProviderRegistry
 #include <qgsdataitemproviderregistry.h>
 %End
   public:
-    static QgsDataItemProviderRegistry * instance();
-
+    QgsDataItemProviderRegistry();
     ~QgsDataItemProviderRegistry();
 
     //! Get list of available providers
@@ -25,7 +24,7 @@ class QgsDataItemProviderRegistry
     void removeProvider( QgsDataItemProvider* provider );
 
   private:
-    QgsDataItemProviderRegistry();
+
     QgsDataItemProviderRegistry( const QgsDataItemProviderRegistry& rh );
 
 };
@@ -5,7 +5,7 @@ class QgsMessageLog : QObject
 %End
 
   public:
-    static QgsMessageLog *instance();
+    QgsMessageLog();
 
     enum MessageLevel
     {
@@ -20,8 +20,6 @@ class QgsMessageLog : QObject
   signals:
     void messageReceived( const QString& message, const QString& tag, MessageLevel level );
 
-  private:
-    QgsMessageLog();
 };
 
 
 
@@ -37,8 +37,7 @@ class QgsPluginLayerRegistry
 
   public:
 
-    /** Means of accessing canonical single instance  */
-    static QgsPluginLayerRegistry* instance();
+    QgsPluginLayerRegistry();
 
     ~QgsPluginLayerRegistry();
 
@@ -62,8 +61,6 @@ class QgsPluginLayerRegistry
 
   private:
 
-    /** Private since instance() creates it */
-    QgsPluginLayerRegistry();
     QgsPluginLayerRegistry( const QgsPluginLayerRegistry& rh );
 
 };
@@ -100,8 +100,8 @@ class QgsRendererRegistry
 
   public:
 
-    //! Returns a pointer to the QgsRendererRegistry singleton
-    static QgsRendererRegistry* instance();
+    QgsRendererRegistry();
+    ~QgsRendererRegistry();
 
     //! Adds a renderer to the registry. Takes ownership of the metadata object.
     //! @param metadata renderer metadata
@@ -128,11 +128,6 @@ class QgsRendererRegistry
     //! @note added in QGIS 2.16
     QStringList renderersList( const QgsVectorLayer* layer ) const;
 
-  protected:
-    //! protected constructor
-    QgsRendererRegistry();
-    ~QgsRendererRegistry();
-
   private:
     QgsRendererRegistry( const QgsRendererRegistry& rh );
     //QgsRendererRegistry& operator=( const QgsRendererRegistry& rh );