diff --git a/platforms.go b/platforms.go
index 75cbf97..e3b5f08 100644
--- a/platforms.go
+++ b/platforms.go
@@ -129,6 +129,16 @@ var (
 	osRe        = regexp.MustCompile(`^([A-Za-z0-9_-]+)(?:\(([A-Za-z0-9_.%-]*)((?:\+[A-Za-z0-9_.%-]+)*)\))?$`)
 )
 
+// validateOSComponent checks that s is a valid OS name. Unlike other
+// specifier components, OS names do not allow dots or OS options.
+func validateOSComponent(s string) error {
+	m := osRe.FindStringSubmatch(s)
+	if m == nil || m[1] != s {
+		return fmt.Errorf("%q must be an OS name matching [A-Za-z0-9_-]+: %w", s, errInvalidArgument)
+	}
+	return nil
+}
+
 // validateSpecifierComponent checks that s is a valid platform specifier
 // component, excluding "." and ".." which would be cleaned by path.Join.
 func validateSpecifierComponent(s string) error {
@@ -484,3 +494,28 @@ func Normalize(platform specs.Platform) specs.Platform {
 
 	return platform
 }
+
+// Validate checks whether the platform is well-formed.
+//
+// OS and Architecture must be non-empty, and all components must be valid
+// platform specifiers. It does not check whether the platform is supported.
+func Validate(platform specs.Platform) error {
+	if platform.OS == "" {
+		return fmt.Errorf("missing OS: %w", errInvalidArgument)
+	}
+	if platform.Architecture == "" {
+		return fmt.Errorf("missing architecture: %w", errInvalidArgument)
+	}
+	if err := validateOSComponent(platform.OS); err != nil {
+		return fmt.Errorf("invalid OS: %w", err)
+	}
+	if err := validateSpecifierComponent(platform.Architecture); err != nil {
+		return fmt.Errorf("invalid architecture: %w", err)
+	}
+	if platform.Variant != "" {
+		if err := validateSpecifierComponent(platform.Variant); err != nil {
+			return fmt.Errorf("invalid variant: %w", err)
+		}
+	}
+	return nil
+}
diff --git a/platforms_test.go b/platforms_test.go
index ffdf9cd..f4385b0 100644
--- a/platforms_test.go
+++ b/platforms_test.go
@@ -17,6 +17,7 @@
 package platforms
 
 import (
+	"errors"
 	"path"
 	"reflect"
 	"runtime"
@@ -743,3 +744,151 @@ func BenchmarkFormatAllOSFeatures(b *testing.B) {
 		})
 	}
 }
+
+func TestValidate(t *testing.T) {
+	tests := []struct {
+		name       string
+		platform   specs.Platform
+		wantErr    bool
+		wantErrMsg string
+	}{
+		{
+			name:    "empty platform",
+			wantErr: true,
+		},
+		{
+			name:     "missing OS",
+			platform: specs.Platform{Architecture: "amd64"},
+			wantErr:  true,
+		},
+		{
+			name:     "missing architecture",
+			platform: specs.Platform{OS: "linux"},
+			wantErr:  true,
+		},
+		{
+			name:     "linux/amd64",
+			platform: specs.Platform{OS: "linux", Architecture: "amd64"},
+		},
+		{
+			name:     "linux/loong64",
+			platform: specs.Platform{OS: "linux", Architecture: "loong64"},
+		},
+		{
+			name:     "unknown OS and architecture",
+			platform: specs.Platform{OS: "customos", Architecture: "customarch"},
+		},
+		{
+			name:     "OS with underscore and hyphen",
+			platform: specs.Platform{OS: "custom_os-v2", Architecture: "amd64"},
+		},
+		{
+			name:     "variant",
+			platform: specs.Platform{OS: "linux", Architecture: "arm", Variant: "v7"},
+		},
+		{
+			name:     "architecture with dot",
+			platform: specs.Platform{OS: "linux", Architecture: "custom.arch"},
+		},
+		{
+			name:     "architecture with underscore and hyphen",
+			platform: specs.Platform{OS: "linux", Architecture: "custom_arch-v2"},
+		},
+		{
+			name:     "variant with dot",
+			platform: specs.Platform{OS: "linux", Architecture: "arm", Variant: "v7.1"},
+		},
+		{
+			name:       "invalid OS",
+			platform:   specs.Platform{OS: "invalid/os", Architecture: "amd64"},
+			wantErr:    true,
+			wantErrMsg: "must be an OS name matching",
+		},
+		{
+			name:       "OS with whitespace",
+			platform:   specs.Platform{OS: "invalid os", Architecture: "amd64"},
+			wantErr:    true,
+			wantErrMsg: "must be an OS name matching",
+		},
+		{
+			name:       "OS with dot",
+			platform:   specs.Platform{OS: "foo.bar", Architecture: "amd64"},
+			wantErr:    true,
+			wantErrMsg: "must be an OS name matching",
+		},
+		{
+			name:       "OS with version",
+			platform:   specs.Platform{OS: "windows(10.0.17763)", Architecture: "amd64"},
+			wantErr:    true,
+			wantErrMsg: "must be an OS name matching",
+		},
+		{
+			name:       "invalid OS character",
+			platform:   specs.Platform{OS: "linux@", Architecture: "amd64"},
+			wantErr:    true,
+			wantErrMsg: "must be an OS name matching",
+		},
+		{
+			name:     "dot OS",
+			platform: specs.Platform{OS: ".", Architecture: "amd64"},
+			wantErr:  true,
+		},
+		{
+			name:     "dot-dot OS",
+			platform: specs.Platform{OS: "..", Architecture: "amd64"},
+			wantErr:  true,
+		},
+		{
+			name:       "invalid architecture",
+			platform:   specs.Platform{OS: "linux", Architecture: "invalid/arch"},
+			wantErr:    true,
+			wantErrMsg: "must match",
+		},
+		{
+			name:       "dot architecture",
+			platform:   specs.Platform{OS: "linux", Architecture: "."},
+			wantErr:    true,
+			wantErrMsg: `must not be "." or ".."`,
+		},
+		{
+			name:       "dot-dot architecture",
+			platform:   specs.Platform{OS: "linux", Architecture: ".."},
+			wantErr:    true,
+			wantErrMsg: `must not be "." or ".."`,
+		},
+		{
+			name:       "invalid variant",
+			platform:   specs.Platform{OS: "linux", Architecture: "arm", Variant: "invalid/variant"},
+			wantErr:    true,
+			wantErrMsg: "must match",
+		},
+		{
+			name:       "dot variant",
+			platform:   specs.Platform{OS: "linux", Architecture: "arm", Variant: "."},
+			wantErr:    true,
+			wantErrMsg: `must not be "." or ".."`,
+		},
+		{
+			name:       "dot-dot variant",
+			platform:   specs.Platform{OS: "linux", Architecture: "arm", Variant: ".."},
+			wantErr:    true,
+			wantErrMsg: `must not be "." or ".."`,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			err := Validate(tc.platform)
+			if tc.wantErr {
+				if !errors.Is(err, errInvalidArgument) {
+					t.Fatalf("Validate(%+v) error = %v, want %v", tc.platform, err, errInvalidArgument)
+				}
+				if tc.wantErrMsg != "" && !strings.Contains(err.Error(), tc.wantErrMsg) {
+					t.Errorf("Validate(%+v) error = %q, want to contain %q", tc.platform, err, tc.wantErrMsg)
+				}
+			} else if err != nil {
+				t.Fatalf("Validate(%+v) unexpected error: %v", tc.platform, err)
+			}
+		})
+	}
+}