diff --git a/CHANGELOG.md b/CHANGELOG.md
index c8a3d1d1b8a..4a6856e059d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -27,6 +27,7 @@
 - Mask password in postgres scaler auto generated metricName. ([PR #1381](https://github.com/kedacore/keda/pull/1381))
 - Bug fix for pending jobs in ScaledJob's accurateScalingStrategy . ([#1323](https://github.com/kedacore/keda/issues/1323))
 - Fix memory leak because of unclosed scalers. ([#1413](https://github.com/kedacore/keda/issues/1413))
+- Automatically determine the RabbitMQ protocol when possible, and support setting the protocl via TriggerAuthentication ([#1459](https://github.com/kedacore/keda/pulls/1459))
 
 ### Breaking Changes
 
diff --git a/pkg/scalers/rabbitmq_scaler.go b/pkg/scalers/rabbitmq_scaler.go
index 54007891a49..ad484ddb28e 100644
--- a/pkg/scalers/rabbitmq_scaler.go
+++ b/pkg/scalers/rabbitmq_scaler.go
@@ -29,7 +29,8 @@ const (
 const (
 	httpProtocol    = "http"
 	amqpProtocol    = "amqp"
-	defaultProtocol = amqpProtocol
+	autoProtocol    = "auto"
+	defaultProtocol = autoProtocol
 )
 
 type rabbitMQScaler struct {
@@ -87,12 +88,14 @@ func parseRabbitMQMetadata(config *ScalerConfig) (*rabbitMQMetadata, error) {
 
 	// Resolve protocol type
 	meta.protocol = defaultProtocol
+	if val, ok := config.AuthParams["protocol"]; ok {
+		meta.protocol = val
+	}
 	if val, ok := config.TriggerMetadata["protocol"]; ok {
-		if val == amqpProtocol || val == httpProtocol {
-			meta.protocol = val
-		} else {
-			return nil, fmt.Errorf("the protocol has to be either `%s` or `%s` but is `%s`", amqpProtocol, httpProtocol, val)
-		}
+		meta.protocol = val
+	}
+	if meta.protocol != amqpProtocol && meta.protocol != httpProtocol && meta.protocol != autoProtocol {
+		return nil, fmt.Errorf("the protocol has to be either `%s`, `%s`, or `%s` but is `%s`", amqpProtocol, httpProtocol, autoProtocol, meta.protocol)
 	}
 
 	// Resolve host value
@@ -107,6 +110,22 @@ func parseRabbitMQMetadata(config *ScalerConfig) (*rabbitMQMetadata, error) {
 		return nil, fmt.Errorf("no host setting given")
 	}
 
+	// If the protocol is auto, check the host scheme.
+	if meta.protocol == autoProtocol {
+		parsedURL, err := url.Parse(meta.host)
+		if err != nil {
+			return nil, fmt.Errorf("can't parse host to find protocol: %s", err)
+		}
+		switch parsedURL.Scheme {
+		case "amqp", "amqps":
+			meta.protocol = amqpProtocol
+		case "http", "https":
+			meta.protocol = httpProtocol
+		default:
+			return nil, fmt.Errorf("unknown host URL scheme `%s`", parsedURL.Scheme)
+		}
+	}
+
 	// Resolve queueName
 	if val, ok := config.TriggerMetadata["queueName"]; ok {
 		meta.queueName = val
diff --git a/pkg/scalers/rabbitmq_scaler_test.go b/pkg/scalers/rabbitmq_scaler_test.go
index dd5f5f86f60..3a37ba05bb1 100644
--- a/pkg/scalers/rabbitmq_scaler_test.go
+++ b/pkg/scalers/rabbitmq_scaler_test.go
@@ -46,6 +46,14 @@ var testRabbitMQMetadata = []parseRabbitMQMetadataTestData{
 	{map[string]string{"queueLength": "10", "queueName": "sample", "host": host, "protocol": "http"}, false, map[string]string{}},
 	// queue name with slashes
 	{map[string]string{"queueLength": "10", "queueName": "namespace/name", "hostFromEnv": host}, false, map[string]string{}},
+	// protocol defined in authParams
+	{map[string]string{"queueName": "sample", "hostFromEnv": host}, false, map[string]string{"protocol": "http"}},
+	// auto protocol and a bad URL
+	{map[string]string{"queueName": "sample", "host": "something://"}, true, map[string]string{}},
+	// auto protocol and an HTTP URL
+	{map[string]string{"queueName": "sample", "host": "http://"}, false, map[string]string{}},
+	// auto protocol and an HTTPS URL
+	{map[string]string{"queueName": "sample", "host": "https://"}, false, map[string]string{}},
 }
 
 var rabbitMQMetricIdentifiers = []rabbitMQMetricIdentifier{
@@ -67,9 +75,9 @@ func TestRabbitMQParseMetadata(t *testing.T) {
 
 var testDefaultQueueLength = []parseRabbitMQMetadataTestData{
 	// use default queueLength
-	{map[string]string{"queueName": "sample", "host": host}, false, map[string]string{}},
+	{map[string]string{"queueName": "sample", "hostFromEnv": host}, false, map[string]string{}},
 	// use default queueLength with includeUnacked
-	{map[string]string{"queueName": "sample", "host": host, "protocol": "http"}, false, map[string]string{}},
+	{map[string]string{"queueName": "sample", "hostFromEnv": host, "protocol": "http"}, false, map[string]string{}},
 }
 
 func TestParseDefaultQueueLength(t *testing.T) {
@@ -171,7 +179,7 @@ func TestGetQueueInfo(t *testing.T) {
 
 func TestRabbitMQGetMetricSpecForScaling(t *testing.T) {
 	for _, testData := range rabbitMQMetricIdentifiers {
-		meta, err := parseRabbitMQMetadata(&ScalerConfig{ResolvedEnv: map[string]string{"myHostSecret": "myHostSecret"}, TriggerMetadata: testData.metadataTestData.metadata, AuthParams: nil})
+		meta, err := parseRabbitMQMetadata(&ScalerConfig{ResolvedEnv: sampleRabbitMqResolvedEnv, TriggerMetadata: testData.metadataTestData.metadata, AuthParams: nil})
 		if err != nil {
 			t.Fatal("Could not parse metadata:", err)
 		}