diff --git a/CHANGELOG.md b/CHANGELOG.md
index f3bf2b1a..b1f7bffd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 ## 1.2.0 (unreleased)
 
 - Made it easier to rotate master key
+- Added `associated_data` option for database fields and files
 - Added `decimal` type
 - Added `encode_attributes` option
 - Fixed deprecation warnings with Rails 7.1
diff --git a/lib/lockbox/box.rb b/lib/lockbox/box.rb
index dc580e2e..62e00c30 100644
--- a/lib/lockbox/box.rb
+++ b/lib/lockbox/box.rb
@@ -1,6 +1,8 @@
 module Lockbox
   class Box
-    def initialize(key: nil, algorithm: nil, encryption_key: nil, decryption_key: nil, padding: false)
+    NOT_SET = Object.new
+
+    def initialize(key: nil, algorithm: nil, encryption_key: nil, decryption_key: nil, padding: false, associated_data: nil)
       raise ArgumentError, "Cannot pass both key and encryption/decryption key" if key && (encryption_key || decryption_key)
 
       key = Lockbox::Utils.decode_key(key) if key
@@ -32,9 +34,11 @@ def initialize(key: nil, algorithm: nil, encryption_key: nil, decryption_key: ni
 
       @algorithm = algorithm
       @padding = padding == true ? 16 : padding
+      @associated_data = associated_data
     end
 
-    def encrypt(message, associated_data: nil)
+    def encrypt(message, associated_data: NOT_SET)
+      associated_data = @associated_data if associated_data == NOT_SET
       message = Lockbox.pad(message, size: @padding) if @padding
       case @algorithm
       when "hybrid"
@@ -53,7 +57,8 @@ def encrypt(message, associated_data: nil)
       nonce + ciphertext
     end
 
-    def decrypt(ciphertext, associated_data: nil)
+    def decrypt(ciphertext, associated_data: NOT_SET)
+      associated_data = @associated_data if associated_data == NOT_SET
       message =
         case @algorithm
         when "hybrid"
diff --git a/test/internal/db/schema.rb b/test/internal/db/schema.rb
index beff8ad1..c4d53fcc 100644
--- a/test/internal/db/schema.rb
+++ b/test/internal/db/schema.rb
@@ -88,6 +88,7 @@
     t.text :conf_ciphertext
     t.text :city_ciphertext
     t.binary :ssn_ciphertext
+    t.text :region_ciphertext
     t.text :state
     t.text :state_ciphertext
     t.text :photo_data
diff --git a/test/model_test.rb b/test/model_test.rb
index 1a5714f2..c1433f9a 100644
--- a/test/model_test.rb
+++ b/test/model_test.rb
@@ -537,6 +537,15 @@ def test_encode
     assert_equal nonce_size + ssn.bytesize + auth_tag_size, user.ssn_ciphertext.bytesize
   end
 
+  def test_associated_data
+    user = User.create!(name: "Test", region: "Data")
+    assert_equal "Data", User.last.region
+    user.update!(name: "New")
+    assert_raises(Lockbox::DecryptionError) do
+      User.last.region
+    end
+  end
+
   def test_attribute_key_encrypted_column
     email = "test@example.org"
     user = User.create!(email: email)
diff --git a/test/support/active_record.rb b/test/support/active_record.rb
index 6e534b72..cc111b67 100644
--- a/test/support/active_record.rb
+++ b/test/support/active_record.rb
@@ -105,6 +105,7 @@ def deserialize(value)
 
   has_encrypted :city, padding: true
   has_encrypted :ssn, encode: false
+  has_encrypted :region, associated_data: -> { name }
 
   has_encrypted :state
 
diff --git a/test/support/mongoid.rb b/test/support/mongoid.rb
index 933b9783..33b57cd0 100644
--- a/test/support/mongoid.rb
+++ b/test/support/mongoid.rb
@@ -13,6 +13,7 @@ class User
   field :phone_ciphertext, type: String
   field :city_ciphertext, type: String
   field :ssn_ciphertext, type: BSON::Binary
+  field :region_ciphertext, type: String
   field :state, type: String
   field :state_ciphertext, type: String
 
@@ -23,6 +24,7 @@ class User
 
   has_encrypted :city, padding: true
   has_encrypted :ssn, encode: false
+  has_encrypted :region, associated_data: -> { name }
   has_encrypted :state
 
   include PhotoUploader::Attachment(:photo)