diff --git a/samlsp/new.go b/samlsp/new.go
index 82bfd835..451a65aa 100644
--- a/samlsp/new.go
+++ b/samlsp/new.go
@@ -15,6 +15,7 @@ import (
 
 // Options represents the parameters for creating a new middleware
 type Options struct {
+	EntityID          string
 	URL               url.URL
 	Key               *rsa.PrivateKey
 	Certificate       *x509.Certificate
@@ -126,6 +127,7 @@ func DefaultServiceProvider(opts Options) saml.ServiceProvider {
 	}
 
 	return saml.ServiceProvider{
+		EntityID:          opts.EntityID,
 		Key:               opts.Key,
 		Certificate:       opts.Certificate,
 		Intermediates:     opts.Intermediates,
diff --git a/service_provider.go b/service_provider.go
index 55435ccf..e64ad065 100644
--- a/service_provider.go
+++ b/service_provider.go
@@ -58,6 +58,9 @@ type SignatureVerifier interface {
 // See the example directory for an example of a web application using
 // the service provider interface.
 type ServiceProvider struct {
+	// Entity ID is optional - if not specified then MetadataURL will be used
+	EntityID string
+
 	// Key is the RSA private key we use to sign requests.
 	Key *rsa.PrivateKey
 
@@ -156,7 +159,7 @@ func (sp *ServiceProvider) Metadata() *EntityDescriptor {
 	}
 
 	return &EntityDescriptor{
-		EntityID:   sp.MetadataURL.String(),
+		EntityID:   firstSet(sp.EntityID, sp.MetadataURL.String()),
 		ValidUntil: validUntil,
 
 		SPSSODescriptors: []SPSSODescriptor{
@@ -316,7 +319,7 @@ func (sp *ServiceProvider) MakeAuthenticationRequest(idpURL string) (*AuthnReque
 		Version:                     "2.0",
 		Issuer: &Issuer{
 			Format: "urn:oasis:names:tc:SAML:2.0:nameid-format:entity",
-			Value:  sp.MetadataURL.String(),
+			Value:  firstSet(sp.EntityID, sp.MetadataURL.String()),
 		},
 		NameIDPolicy: &NameIDPolicy{
 			AllowCreate: &allowCreate,
@@ -656,13 +659,14 @@ func (sp *ServiceProvider) validateAssertion(assertion *Assertion, possibleReque
 	}
 
 	audienceRestrictionsValid := len(assertion.Conditions.AudienceRestrictions) == 0
+	audience := firstSet(sp.EntityID, sp.MetadataURL.String())
 	for _, audienceRestriction := range assertion.Conditions.AudienceRestrictions {
-		if audienceRestriction.Audience.Value == sp.MetadataURL.String() {
+		if audienceRestriction.Audience.Value == audience {
 			audienceRestrictionsValid = true
 		}
 	}
 	if !audienceRestrictionsValid {
-		return fmt.Errorf("assertion Conditions AudienceRestriction does not contain %q", sp.MetadataURL.String())
+		return fmt.Errorf("assertion Conditions AudienceRestriction does not contain %q", audience)
 	}
 	return nil
 }
@@ -802,7 +806,7 @@ func (sp *ServiceProvider) MakeLogoutRequest(idpURL, nameID string) (*LogoutRequ
 		Destination:  idpURL,
 		Issuer: &Issuer{
 			Format: "urn:oasis:names:tc:SAML:2.0:nameid-format:entity",
-			Value:  sp.MetadataURL.String(),
+			Value:  firstSet(sp.EntityID, sp.MetadataURL.String()),
 		},
 		NameID: &NameID{
 			Format:          sp.nameIDFormat(),
@@ -935,3 +939,10 @@ func (sp *ServiceProvider) validateLogoutResponse(resp *LogoutResponse) error {
 
 	return nil
 }
+
+func firstSet(a, b string) string {
+	if a == "" {
+		return b
+	}
+	return a
+}
diff --git a/service_provider_test.go b/service_provider_test.go
index ce370edc..005e8453 100644
--- a/service_provider_test.go
+++ b/service_provider_test.go
@@ -163,6 +163,29 @@ func TestCanProduceMetadataNoSigningKey(t *testing.T) {
 		string(spMetadata))
 }
 
+func TestCanProduceMetadataEntityID(t *testing.T) {
+	test := NewServiceProviderTest()
+	s := ServiceProvider{
+		EntityID:    "spn:11111111-2222-3333-4444-555555555555",
+		MetadataURL: mustParseURL("https://example.com/saml2/metadata"),
+		AcsURL:      mustParseURL("https://example.com/saml2/acs"),
+		IDPMetadata: &EntityDescriptor{},
+	}
+	err := xml.Unmarshal([]byte(test.IDPMetadata), &s.IDPMetadata)
+	assert.NoError(t, err)
+
+	spMetadata, err := xml.MarshalIndent(s.Metadata(), "", "  ")
+	assert.NoError(t, err)
+	assert.Equal(t, ""+
+		"<EntityDescriptor xmlns=\"urn:oasis:names:tc:SAML:2.0:metadata\" validUntil=\"2015-12-03T01:57:09Z\" entityID=\"spn:11111111-2222-3333-4444-555555555555\">\n"+
+		"  <SPSSODescriptor xmlns=\"urn:oasis:names:tc:SAML:2.0:metadata\" validUntil=\"2015-12-03T01:57:09Z\" protocolSupportEnumeration=\"urn:oasis:names:tc:SAML:2.0:protocol\" AuthnRequestsSigned=\"false\" WantAssertionsSigned=\"true\">\n"+
+		"    <SingleLogoutService Binding=\"urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST\" Location=\"\"></SingleLogoutService>\n"+
+		"    <AssertionConsumerService Binding=\"urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST\" Location=\"https://example.com/saml2/acs\" index=\"1\"></AssertionConsumerService>\n"+
+		"  </SPSSODescriptor>\n"+
+		"</EntityDescriptor>",
+		string(spMetadata))
+}
+
 func TestSPCanProduceRedirectRequest(t *testing.T) {
 	test := NewServiceProviderTest()
 	TimeNow = func() time.Time {