diff --git a/gems/aws-sdk-core/CHANGELOG.md b/gems/aws-sdk-core/CHANGELOG.md
index 718762649a4..c9783720c9e 100644
--- a/gems/aws-sdk-core/CHANGELOG.md
+++ b/gems/aws-sdk-core/CHANGELOG.md
@@ -1,6 +1,8 @@
 Unreleased Changes
 ------------------
 
+* Feature - Reduce memory usage of loaded service APIs by allocating shape metadata Hashes on first write.
+
 3.264.0 (2026-11-04)
 ------------------
 
diff --git a/gems/aws-sdk-core/lib/seahorse/model/shapes.rb b/gems/aws-sdk-core/lib/seahorse/model/shapes.rb
index 5475c77bbe3..ef4418832f9 100644
--- a/gems/aws-sdk-core/lib/seahorse/model/shapes.rb
+++ b/gems/aws-sdk-core/lib/seahorse/model/shapes.rb
@@ -9,7 +9,7 @@ module Shapes
       class ShapeRef
 
         def initialize(options = {})
-          @metadata = {}
+          @metadata = nil
           @required = false
           @deprecated = false
           @location = nil
@@ -84,7 +84,7 @@ def location_name= location_name
 
         # Gets metadata for the given `key`.
         def [](key)
-          if @metadata.key?(key.to_s)
+          if @metadata&.key?(key.to_s)
             @metadata[key.to_s]
           elsif @shape
             @shape[key.to_s]
@@ -93,7 +93,7 @@ def [](key)
 
         # Sets metadata for the given `key`.
         def []=(key, value)
-          @metadata[key.to_s] = value
+          (@metadata ||= {})[key.to_s] = value
         end
 
       end
@@ -101,7 +101,7 @@ def []=(key, value)
       class Shape
 
         def initialize(options = {})
-          @metadata = {}
+          @metadata = nil
           options.each_pair do |key, value|
             if respond_to?("#{key}=")
               send("#{key}=", value)
@@ -122,12 +122,12 @@ def initialize(options = {})
 
         # Gets metadata for the given `key`.
         def [](key)
-          @metadata[key.to_s]
+          @metadata && @metadata[key.to_s]
         end
 
         # Sets metadata for the given `key`.
         def []=(key, value)
-          @metadata[key.to_s] = value
+          (@metadata ||= {})[key.to_s] = value
         end
 
       end
diff --git a/gems/aws-sdk-core/spec/seahorse/model/shapes_spec.rb b/gems/aws-sdk-core/spec/seahorse/model/shapes_spec.rb
index 40815306285..3e38505471d 100644
--- a/gems/aws-sdk-core/spec/seahorse/model/shapes_spec.rb
+++ b/gems/aws-sdk-core/spec/seahorse/model/shapes_spec.rb
@@ -52,6 +52,12 @@ module Shapes
           expect(ref['key']).to eq('value')
         end
 
+        it 'returns nil for metadata that was never set' do
+          expect(ShapeRef.new[:key]).to be(nil)
+          expect(ShapeRef.new(shape: Shape.new)[:key]).to be(nil)
+          expect(Shape.new[:key]).to be(nil)
+        end
+
         it 'can be populated via .new' do
           shape = double('shape')
           ref = ShapeRef.new(