diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index a7af51f83ecdc189c0e09766ad5785113c16c84d..cbbb8597c200560c8ef792b6c0f526e5a83c424b 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,5 +1,33 @@
 ## Rails 6.0.0.alpha (Unreleased) ##
 
+*   `ActiveSupport::Inflector#ordinal` and `ActiveSupport::Inflector#ordinalize` now support
+    translations through I18n.
+
+        # locale/fr.rb
+
+        {
+          fr: {
+            number: {
+              nth: {
+                ordinals: lambda do |_key, number:, **_options|
+                  if number.to_i.abs == 1
+                    'er'
+                  else
+                    'e'
+                  end
+                end,
+
+                ordinalized: lambda do |_key, number:, **_options|
+                  "#{number}#{ActiveSupport::Inflector.ordinal(number)}"
+                end
+              }
+            }
+          }
+        }
+
+
+    *Christian Blais*
+
 *   Add `:private` option to ActiveSupport's `Module#delegate`
     in order to delegate methods as private:
 
diff --git a/activesupport/lib/active_support/i18n.rb b/activesupport/lib/active_support/i18n.rb
index d60b3eff3063020440836435426c446d4af038d2..39dab1cc71aa3be015665cd540188efebe18849c 100644
--- a/activesupport/lib/active_support/i18n.rb
+++ b/activesupport/lib/active_support/i18n.rb
@@ -13,3 +13,4 @@
 
 ActiveSupport.run_load_hooks(:i18n)
 I18n.load_path << File.expand_path("locale/en.yml", __dir__)
+I18n.load_path << File.expand_path("locale/en.rb", __dir__)
diff --git a/activesupport/lib/active_support/inflector/methods.rb b/activesupport/lib/active_support/inflector/methods.rb
index 7e782e2a93331f12d7c6eb164620434145c9c4b3..339b93b8da05c97f81995eab4a95c8b5d80b0281 100644
--- a/activesupport/lib/active_support/inflector/methods.rb
+++ b/activesupport/lib/active_support/inflector/methods.rb
@@ -341,18 +341,7 @@ def safe_constantize(camel_cased_word)
     #   ordinal(-11)   # => "th"
     #   ordinal(-1021) # => "st"
     def ordinal(number)
-      abs_number = number.to_i.abs
-
-      if (11..13).include?(abs_number % 100)
-        "th"
-      else
-        case abs_number % 10
-        when 1; "st"
-        when 2; "nd"
-        when 3; "rd"
-        else    "th"
-        end
-      end
+      I18n.translate("number.nth.ordinals", number: number)
     end
 
     # Turns a number into an ordinal string used to denote the position in an
@@ -365,7 +354,7 @@ def ordinal(number)
     #   ordinalize(-11)   # => "-11th"
     #   ordinalize(-1021) # => "-1021st"
     def ordinalize(number)
-      "#{number}#{ordinal(number)}"
+      I18n.translate("number.nth.ordinalized", number: number)
     end
 
     private
diff --git a/activesupport/lib/active_support/locale/en.rb b/activesupport/lib/active_support/locale/en.rb
new file mode 100644
index 0000000000000000000000000000000000000000..26c2280c95e116a55355d5cbcc3fd01ba51eef4e
--- /dev/null
+++ b/activesupport/lib/active_support/locale/en.rb
@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+{
+  en: {
+    number: {
+      nth: {
+        ordinals: lambda do |_key, number:, **_options|
+          abs_number = number.to_i.abs
+
+          if (11..13).cover?(abs_number % 100)
+            "th"
+          else
+            case abs_number % 10
+            when 1 then "st"
+            when 2 then "nd"
+            when 3 then "rd"
+            else "th"
+            end
+          end
+        end,
+
+        ordinalized: lambda do |_key, number:, **_options|
+          "#{number}#{ActiveSupport::Inflector.ordinal(number)}"
+        end
+      }
+    }
+  }
+}