diff --git a/cmd/prometheus/config.go b/cmd/prometheus/config.go
index af124cc26..568bcaa4d 100644
--- a/cmd/prometheus/config.go
+++ b/cmd/prometheus/config.go
@@ -34,6 +34,8 @@ import (
 	"github.com/prometheus/prometheus/storage/local/index"
 	"github.com/prometheus/prometheus/storage/remote"
 	"github.com/prometheus/prometheus/web"
+	"github.com/prometheus/prometheus/config"
+	"github.com/prometheus/common/model"
 )
 
 // cfg contains immutable configuration parameters for a running Prometheus
@@ -365,6 +367,44 @@ func validateAlertmanagerURL(u string) error {
 	return nil
 }
 
+func parseAlertmanagerURLToConfig(us string) (*config.AlertmanagerConfig, error) {
+	u, err := url.Parse(us)
+	if err != nil {
+		return nil, err
+	}
+	acfg := &config.AlertmanagerConfig{
+		Scheme:     u.Scheme,
+		PathPrefix: u.Path,
+		Timeout:    cfg.notifierTimeout,
+		ServiceDiscoveryConfig: config.ServiceDiscoveryConfig{
+			StaticConfigs: []*config.TargetGroup{
+				{
+					Targets: []model.LabelSet{
+						{
+							model.AddressLabel: model.LabelValue(u.Host),
+						},
+					},
+				},
+			},
+		},
+	}
+
+	if u.User != nil {
+		acfg.HTTPClientConfig = config.HTTPClientConfig{
+			BasicAuth: &config.BasicAuth{
+				Username: u.User.Username(),
+			},
+		}
+
+		if password, isSet := u.User.Password(); isSet {
+			acfg.HTTPClientConfig.BasicAuth.Password = password
+		}
+	}
+
+	return acfg, nil
+}
+
+
 var helpTmpl = `
 usage: prometheus [<args>]
 {{ range $cat, $flags := . }}{{ if ne $cat "." }} == {{ $cat | upper }} =={{ end }}
diff --git a/cmd/prometheus/config_test.go b/cmd/prometheus/config_test.go
index 1b7964721..406243456 100644
--- a/cmd/prometheus/config_test.go
+++ b/cmd/prometheus/config_test.go
@@ -80,3 +80,46 @@ func TestParse(t *testing.T) {
 		}
 	}
 }
+
+func TestParseAlertmanagerURLToConfig(t *testing.T) {
+	tests := []struct {
+		url string
+		username string
+		password string
+	}{
+		{
+			url: "http://alertmanager.company.com",
+			username: "",
+			password: "",
+		},
+		{
+			url: "https://user:password@alertmanager.company.com",
+			username: "user",
+			password: "password",
+		},
+	}
+
+	for i, test := range tests {
+		acfg, err := parseAlertmanagerURLToConfig(test.url)
+		if err != nil {
+			t.Errorf("%d. expected alertmanager URL to be valid, got %s", i, err)
+		}
+
+		if acfg.HTTPClientConfig.BasicAuth != nil {
+			if test.username != acfg.HTTPClientConfig.BasicAuth.Username {
+				t.Errorf("%d. expected alertmanagerConfig username to be %q, got %q",
+					i, test.username, acfg.HTTPClientConfig.BasicAuth.Username)
+			}
+
+			if test.password != acfg.HTTPClientConfig.BasicAuth.Password {
+				t.Errorf("%d. expected alertmanagerConfig password to be %q, got %q", i,
+					test.password, acfg.HTTPClientConfig.BasicAuth.Username)
+			}
+			continue
+		}
+
+		if test.username != "" || test.password != "" {
+			t.Errorf("%d. expected alertmanagerConfig to have basicAuth filled, but was not", i)
+		}
+	}
+}
\ No newline at end of file
diff --git a/cmd/prometheus/main.go b/cmd/prometheus/main.go
index c6ce558db..de1c348a0 100644
--- a/cmd/prometheus/main.go
+++ b/cmd/prometheus/main.go
@@ -18,7 +18,6 @@ import (
 	"flag"
 	"fmt"
 	_ "net/http/pprof" // Comment this line to disable pprof endpoint.
-	"net/url"
 	"os"
 	"os/signal"
 	"syscall"
@@ -26,7 +25,6 @@ import (
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/common/log"
-	"github.com/prometheus/common/model"
 	"github.com/prometheus/common/version"
 	"golang.org/x/net/context"
 
@@ -264,26 +262,10 @@ func reloadConfig(filename string, rls ...Reloadable) (err error) {
 
 	// Add AlertmanagerConfigs for legacy Alertmanager URL flags.
 	for us := range cfg.alertmanagerURLs {
-		u, err := url.Parse(us)
+		acfg, err := parseAlertmanagerURLToConfig(us)
 		if err != nil {
 			return err
 		}
-		acfg := &config.AlertmanagerConfig{
-			Scheme:     u.Scheme,
-			PathPrefix: u.Path,
-			Timeout:    cfg.notifierTimeout,
-			ServiceDiscoveryConfig: config.ServiceDiscoveryConfig{
-				StaticConfigs: []*config.TargetGroup{
-					{
-						Targets: []model.LabelSet{
-							{
-								model.AddressLabel: model.LabelValue(u.Host),
-							},
-						},
-					},
-				},
-			},
-		}
 		conf.AlertingConfig.AlertmanagerConfigs = append(conf.AlertingConfig.AlertmanagerConfigs, acfg)
 	}