diff --git a/pkg/sif/testdata/TestReplace/ReplaceImageManifest.golden b/pkg/sif/testdata/TestReplace/ReplaceImageManifest.golden
new file mode 100644
index 0000000..a650261
Binary files /dev/null and b/pkg/sif/testdata/TestReplace/ReplaceImageManifest.golden differ
diff --git a/pkg/sif/testdata/TestReplace/ReplaceImageManifestList.golden b/pkg/sif/testdata/TestReplace/ReplaceImageManifestList.golden
new file mode 100644
index 0000000..0dba8c6
Binary files /dev/null and b/pkg/sif/testdata/TestReplace/ReplaceImageManifestList.golden differ
diff --git a/pkg/sif/testdata/TestReplace/ReplaceImageNoMatch.golden b/pkg/sif/testdata/TestReplace/ReplaceImageNoMatch.golden
new file mode 100644
index 0000000..2d28e07
Binary files /dev/null and b/pkg/sif/testdata/TestReplace/ReplaceImageNoMatch.golden differ
diff --git a/pkg/sif/testdata/TestReplace/ReplaceIndexManifest.golden b/pkg/sif/testdata/TestReplace/ReplaceIndexManifest.golden
new file mode 100644
index 0000000..cdec4e3
Binary files /dev/null and b/pkg/sif/testdata/TestReplace/ReplaceIndexManifest.golden differ
diff --git a/pkg/sif/testdata/TestReplace/ReplaceIndexManifestList.golden b/pkg/sif/testdata/TestReplace/ReplaceIndexManifestList.golden
new file mode 100644
index 0000000..bd70cbf
Binary files /dev/null and b/pkg/sif/testdata/TestReplace/ReplaceIndexManifestList.golden differ
diff --git a/pkg/sif/testdata/TestReplace/ReplaceIndexNoMatch.golden b/pkg/sif/testdata/TestReplace/ReplaceIndexNoMatch.golden
new file mode 100644
index 0000000..8940e8b
Binary files /dev/null and b/pkg/sif/testdata/TestReplace/ReplaceIndexNoMatch.golden differ
diff --git a/pkg/sif/update.go b/pkg/sif/update.go
index aac1007..20fa460 100644
--- a/pkg/sif/update.go
+++ b/pkg/sif/update.go
@@ -408,17 +408,27 @@ func (f *OCIFileImage) append(add mutate.Appendable, opts ...AppendOpt) error {
 		return err
 	}
 
+	ri, err = appendToIndex(ri, add, ao)
+	if err != nil {
+		return err
+	}
+
+	return f.UpdateRootIndex(ri, OptUpdateTempDir(ao.tempDir))
+}
+
+func appendToIndex(base v1.ImageIndex, add mutate.Appendable, ao appendOpts) (v1.ImageIndex, error) {
 	ia := mutate.IndexAddendum{Add: add}
 
+	var err error
 	if ao.ref != nil {
-		ri, err = removeRefAnnotation(ri, ao.ref)
+		base, err = removeRefAnnotation(base, ao.ref)
 		if err != nil {
-			return err
+			return nil, err
 		}
 
 		d, err := partial.Descriptor(add)
 		if err != nil {
-			return err
+			return nil, err
 		}
 		if d.Annotations != nil {
 			ia.Annotations = maps.Clone(d.Annotations)
@@ -427,9 +437,8 @@ func (f *OCIFileImage) append(add mutate.Appendable, opts ...AppendOpt) error {
 		}
 		ia.Annotations[imagespec.AnnotationRefName] = ao.ref.Name()
 	}
-	ri = mutate.AppendManifests(ri, ia)
 
-	return f.UpdateRootIndex(ri, OptUpdateTempDir(ao.tempDir))
+	return mutate.AppendManifests(base, ia), nil
 }
 
 // removeRefAnnotation removes an existing "org.opencontainers.image.ref.name"
@@ -462,3 +471,42 @@ func (f *OCIFileImage) RemoveManifests(matcher match.Matcher) error {
 	}
 	return f.UpdateRootIndex(mutate.RemoveManifests(ri, matcher))
 }
+
+// ReplaceImage writes img to the SIF, replacing any existing manifest that is
+// selected by the matcher. Any blobs in the SIF that are no longer referenced
+// are removed from the SIF.
+func (f *OCIFileImage) ReplaceImage(img v1.Image, matcher match.Matcher, opts ...AppendOpt) error {
+	return f.replace(img, matcher, opts...)
+}
+
+// ReplaceIndex writes ii to the SIF, replacing any existing manifest that is
+// selected by the matcher. Any blobs in the SIF that are no longer referenced
+// are removed from the SIF.
+func (f *OCIFileImage) ReplaceIndex(ii v1.ImageIndex, matcher match.Matcher, opts ...AppendOpt) error {
+	return f.replace(ii, matcher, opts...)
+}
+
+func (f *OCIFileImage) replace(add mutate.Appendable, matcher match.Matcher, opts ...AppendOpt) error {
+	ao := appendOpts{
+		tempDir: os.TempDir(),
+	}
+	for _, opt := range opts {
+		if err := opt(&ao); err != nil {
+			return err
+		}
+	}
+
+	ri, err := f.RootIndex()
+	if err != nil {
+		return err
+	}
+
+	ri = mutate.RemoveManifests(ri, matcher)
+
+	ri, err = appendToIndex(ri, add, ao)
+	if err != nil {
+		return err
+	}
+
+	return f.UpdateRootIndex(ri, OptUpdateTempDir(ao.tempDir))
+}
diff --git a/pkg/sif/update_test.go b/pkg/sif/update_test.go
index 43bd840..2cb1ca0 100644
--- a/pkg/sif/update_test.go
+++ b/pkg/sif/update_test.go
@@ -439,3 +439,95 @@ func TestRemoveManifests(t *testing.T) {
 		})
 	}
 }
+
+//nolint:dupl
+func TestReplace(t *testing.T) {
+	r := rand.NewSource(randomSeed)
+	newImage, err := random.Image(64, 1, random.WithSource(r))
+	if err != nil {
+		t.Fatal(err)
+	}
+	newIndex, err := random.Index(64, 1, 1, random.WithSource(r))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	replaceImage := func(ofi *sif.OCIFileImage, m match.Matcher) error { return ofi.ReplaceImage(newImage, m) }
+	replaceIndex := func(ofi *sif.OCIFileImage, m match.Matcher) error { return ofi.ReplaceIndex(newIndex, m) }
+	tests := []struct {
+		name        string
+		base        string
+		replacement func(ofi *sif.OCIFileImage, m match.Matcher) error
+		matcher     match.Matcher
+	}{
+		{
+			name:        "ReplaceImageManifest",
+			base:        "hello-world-docker-v2-manifest",
+			replacement: replaceImage,
+			matcher:     match.Platforms(v1.Platform{OS: "linux", Architecture: "arm64", Variant: "v8"}),
+		},
+		{
+			name:        "ReplaceImageManifestList",
+			base:        "hello-world-docker-v2-manifest-list",
+			replacement: replaceImage,
+			matcher:     match.Platforms(v1.Platform{OS: "linux", Architecture: "arm64", Variant: "v8"}),
+		},
+		{
+			name:        "ReplaceImageNoMatch",
+			base:        "hello-world-docker-v2-manifest",
+			replacement: replaceImage,
+			matcher:     match.Platforms(v1.Platform{OS: "linux", Architecture: "m68k"}),
+		},
+		{
+			name:        "ReplaceIndexManifest",
+			base:        "hello-world-docker-v2-manifest",
+			replacement: replaceIndex,
+			matcher:     match.Platforms(v1.Platform{OS: "linux", Architecture: "arm64", Variant: "v8"}),
+		},
+		{
+			name:        "ReplaceIndexManifestList",
+			base:        "hello-world-docker-v2-manifest-list",
+			replacement: replaceIndex,
+			matcher:     match.Platforms(v1.Platform{OS: "linux", Architecture: "arm64", Variant: "v8"}),
+		},
+		{
+			name:        "ReplaceIndexNoMatch",
+			base:        "hello-world-docker-v2-manifest",
+			replacement: replaceIndex,
+			matcher:     match.Platforms(v1.Platform{OS: "linux", Architecture: "m68k"}),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			sifPath := corpus.SIF(t, tt.base, sif.OptWriteWithSpareDescriptorCapacity(8))
+			fi, err := ssif.LoadContainerFromPath(sifPath)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			ofi, err := sif.FromFileImage(fi)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if err := tt.replacement(ofi, tt.matcher); err != nil {
+				t.Fatal(err)
+			}
+
+			if err := fi.UnloadContainer(); err != nil {
+				t.Fatal(err)
+			}
+
+			b, err := os.ReadFile(sifPath)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			g := goldie.New(t,
+				goldie.WithTestNameForDir(true),
+			)
+
+			g.Assert(t, tt.name, b)
+		})
+	}
+}