diff --git a/lib/rubyzen/collections/classes_collection.rb b/lib/rubyzen/collections/classes_collection.rb
index 5073a4b..12c5a88 100644
--- a/lib/rubyzen/collections/classes_collection.rb
+++ b/lib/rubyzen/collections/classes_collection.rb
@@ -24,6 +24,14 @@ def attributes
         AttributesCollection.new(all_attributes)
       end
 
+      # Returns all constant references and assignments across every class.
+      #
+      # @return [ConstantsCollection]
+      def constants
+        all_constants = flat_map(&:constants)
+        ConstantsCollection.new(all_constants)
+      end
+
       # Returns all macro invocations across every class.
       #
       # @return [MacrosCollection]
diff --git a/spec/collections/classes_collection_spec.rb b/spec/collections/classes_collection_spec.rb
index 22189dc..3170bc1 100644
--- a/spec/collections/classes_collection_spec.rb
+++ b/spec/collections/classes_collection_spec.rb
@@ -4,6 +4,7 @@
   let(:file) do
     parse_ruby(<<~RUBY)
       class Foo < ApplicationController
+        DEFAULT_NAME = 'name'
         attr_reader :name
         validates_required :name
 
@@ -37,6 +38,14 @@ def compute; end
     end
   end
 
+  describe '#constants' do
+    it 'returns all constants across classes' do
+      constants = classes.constants
+      expect(constants).to be_a(Rubyzen::Collections::ConstantsCollection)
+      expect(constants.map(&:name)).to include('DEFAULT_NAME')
+    end
+  end
+
   describe '#macros' do
     it 'returns all macros across classes' do
       macros = classes.macros