diff --git a/.dockerignore b/.dockerignore
new file mode 100644
index 000000000..32d134f7d
--- /dev/null
+++ b/.dockerignore
@@ -0,0 +1,3 @@
+data/
+prometheus
+promtool
diff --git a/config/config.go b/config/config.go
index 46fbc9e75..1b8d05441 100644
--- a/config/config.go
+++ b/config/config.go
@@ -97,6 +97,11 @@ var (
 	DefaultServersetSDConfig = ServersetSDConfig{
 		Timeout: Duration(10 * time.Second),
 	}
+
+	// DefaultMarathonSDConfig is the default Marathon SD configuration.
+	DefaultMarathonSDConfig = MarathonSDConfig{
+		RefreshInterval: Duration(30 * time.Second),
+	}
 )
 
 // Config is the top-level configuration for Prometheus's config files.
@@ -239,6 +244,8 @@ type ScrapeConfig struct {
 	ConsulSDConfigs []*ConsulSDConfig `yaml:"consul_sd_configs,omitempty"`
 	// List of Serverset service discovery configurations.
 	ServersetSDConfigs []*ServersetSDConfig `yaml:"serverset_sd_configs,omitempty"`
+	// MarathonSDConfigs is a list of Marathon service discovery configurations.
+	MarathonSDConfigs []*MarathonSDConfig `yaml:"marathon_sd_configs,omitempty"`
 
 	// List of target relabel configurations.
 	RelabelConfigs []*RelabelConfig `yaml:"relabel_configs,omitempty"`
@@ -474,6 +481,29 @@ func (c *ServersetSDConfig) UnmarshalYAML(unmarshal func(interface{}) error) err
 	return checkOverflow(c.XXX, "serverset_sd_config")
 }
 
+// MarathonSDConfig is the configuration for services running on Marathon.
+type MarathonSDConfig struct {
+	Servers         []string `yaml:"servers,omitempty"`
+	RefreshInterval Duration `yaml:"refresh_interval,omitempty"`
+
+	// Catches all undefined fields and must be empty after parsing.
+	XXX map[string]interface{} `yaml:",inline"`
+}
+
+// UnmarshalYAML implements the yaml.Unmarshaler interface.
+func (c *MarathonSDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	*c = DefaultMarathonSDConfig
+	type plain MarathonSDConfig
+	err := unmarshal((*plain)(c))
+	if err != nil {
+		return err
+	}
+	if len(c.Servers) == 0 {
+		return fmt.Errorf("Marathon SD config must contain at least one Marathon server")
+	}
+	return checkOverflow(c.XXX, "marathon_sd_config")
+}
+
 // RelabelAction is the action to be performed on relabeling.
 type RelabelAction string
 
@@ -510,7 +540,7 @@ type RelabelConfig struct {
 	// Separator is the string between concatenated values from the source labels.
 	Separator string `yaml:"separator,omitempty"`
 	// Regex against which the concatenation is matched.
-	Regex *Regexp `yaml:"regex",omitempty`
+	Regex *Regexp `yaml:"regex,omitempty"`
 	// Modulus to take of the hash of concatenated values from the source labels.
 	Modulus uint64 `yaml:"modulus,omitempty"`
 	// The label to which the resulting string is written in a replacement.
diff --git a/retrieval/discovery/marathon.go b/retrieval/discovery/marathon.go
new file mode 100644
index 000000000..5fc4d07a9
--- /dev/null
+++ b/retrieval/discovery/marathon.go
@@ -0,0 +1,98 @@
+package discovery
+
+import (
+	"time"
+
+	"github.com/prometheus/log"
+	"github.com/prometheus/prometheus/config"
+	"github.com/prometheus/prometheus/retrieval/discovery/marathon"
+)
+
+// MarathonDiscovery provides service discovery based on a Marathon instance.
+type MarathonDiscovery struct {
+	servers         []string
+	refreshInterval time.Duration
+	done            chan struct{}
+	lastRefresh     map[string]*config.TargetGroup
+	client          marathon.AppListClient
+}
+
+// NewMarathonDiscovery creates a new Marathon based discovery.
+func NewMarathonDiscovery(conf *config.MarathonSDConfig) *MarathonDiscovery {
+	return &MarathonDiscovery{
+		servers:         conf.Servers,
+		refreshInterval: time.Duration(conf.RefreshInterval),
+		done:            make(chan struct{}),
+		client:          marathon.FetchMarathonApps,
+	}
+}
+
+// Sources implements the TargetProvider interface.
+func (md *MarathonDiscovery) Sources() []string {
+	var sources []string
+	tgroups, err := md.fetchTargetGroups()
+	if err == nil {
+		for source := range tgroups {
+			sources = append(sources, source)
+		}
+	}
+	return sources
+}
+
+// Run implements the TargetProvider interface.
+func (md *MarathonDiscovery) Run(ch chan<- *config.TargetGroup) {
+	defer close(ch)
+
+	for {
+		select {
+		case <-md.done:
+			log.Debug("Shutting down marathon discovery.")
+			return
+		case <-time.After(md.refreshInterval):
+			err := md.updateServices(ch)
+			if err != nil {
+				log.Errorf("Error while updating services: %s", err)
+			}
+		}
+	}
+}
+
+// Stop implements the TargetProvider interface.
+func (md *MarathonDiscovery) Stop() {
+	md.done <- struct{}{}
+}
+
+func (md *MarathonDiscovery) updateServices(ch chan<- *config.TargetGroup) error {
+	targetMap, err := md.fetchTargetGroups()
+	if err != nil {
+		return err
+	}
+
+	// Update services which are still present
+	for _, tg := range targetMap {
+		ch <- tg
+	}
+
+	// Remove services which did disappear
+	for source := range md.lastRefresh {
+		_, ok := targetMap[source]
+		if !ok {
+			log.Debugf("Removing group for %s", source)
+			ch <- &config.TargetGroup{Source: source}
+		}
+	}
+
+	md.lastRefresh = targetMap
+	return nil
+}
+
+func (md *MarathonDiscovery) fetchTargetGroups() (map[string]*config.TargetGroup, error) {
+	url := marathon.RandomAppsURL(md.servers)
+	apps, err := md.client(url)
+	if err != nil {
+		return nil, err
+	}
+
+	groups := marathon.AppsToTargetGroups(apps)
+	return groups, nil
+}
diff --git a/retrieval/discovery/marathon/client.go b/retrieval/discovery/marathon/client.go
new file mode 100644
index 000000000..52ccbbf7a
--- /dev/null
+++ b/retrieval/discovery/marathon/client.go
@@ -0,0 +1,34 @@
+package marathon
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"net/http"
+)
+
+// AppListClient defines a function that can be used to get an application list from marathon.
+type AppListClient func(url string) (*AppList, error)
+
+// FetchMarathonApps requests a list of applications from a marathon server.
+func FetchMarathonApps(url string) (*AppList, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, err
+	}
+
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	return parseAppJSON(body)
+}
+
+func parseAppJSON(body []byte) (*AppList, error) {
+	apps := &AppList{}
+	err := json.Unmarshal(body, apps)
+	if err != nil {
+		return nil, err
+	}
+	return apps, nil
+}
diff --git a/retrieval/discovery/marathon/constants.go b/retrieval/discovery/marathon/constants.go
new file mode 100644
index 000000000..7b761a660
--- /dev/null
+++ b/retrieval/discovery/marathon/constants.go
@@ -0,0 +1,16 @@
+package marathon
+
+import (
+	"github.com/prometheus/client_golang/model"
+)
+
+const (
+	// AppLabel is used for the name of the app in Marathon.
+	AppLabel model.LabelName = "__meta_marathon_app"
+
+	// ImageLabel is the label that is used for the docker image running the service.
+	ImageLabel model.LabelName = "__meta_marathon_image"
+
+	// TaskLabel contains the mesos task name of the app instance.
+	TaskLabel model.LabelName = "__meta_marathon_task"
+)
diff --git a/retrieval/discovery/marathon/conversion.go b/retrieval/discovery/marathon/conversion.go
new file mode 100644
index 000000000..eace6cb2d
--- /dev/null
+++ b/retrieval/discovery/marathon/conversion.go
@@ -0,0 +1,76 @@
+package marathon
+
+import (
+	"fmt"
+	"strings"
+
+	clientmodel "github.com/prometheus/client_golang/model"
+
+	"github.com/prometheus/prometheus/config"
+)
+
+// AppsToTargetGroups takes an array of Marathon apps and converts them into target groups.
+func AppsToTargetGroups(apps *AppList) map[string]*config.TargetGroup {
+	tgroups := map[string]*config.TargetGroup{}
+	for _, a := range apps.Apps {
+		if isValidApp(&a) {
+			group := createTargetGroup(&a)
+			tgroups[group.Source] = group
+		}
+	}
+	return tgroups
+}
+
+func createTargetGroup(app *App) *config.TargetGroup {
+	var (
+		targets = targetsForApp(app)
+		source  = targetGroupName(app)
+		appName = clientmodel.LabelValue(sanitizeName(app.ID))
+		image   = clientmodel.LabelValue(imageName(app))
+	)
+	return &config.TargetGroup{
+		Targets: targets,
+		Labels: clientmodel.LabelSet{
+			AppLabel:   appName,
+			ImageLabel: image,
+		},
+		Source: source,
+	}
+}
+
+func targetsForApp(app *App) []clientmodel.LabelSet {
+	targets := make([]clientmodel.LabelSet, 0, len(app.Tasks))
+	for _, t := range app.Tasks {
+		target := targetForTask(&t)
+		targets = append(targets, clientmodel.LabelSet{
+			clientmodel.AddressLabel: clientmodel.LabelValue(target),
+			TaskLabel:                clientmodel.LabelValue(sanitizeName(t.ID)),
+		})
+	}
+	return targets
+}
+
+func imageName(app *App) string {
+	return app.Container.Docker.Image
+}
+
+func targetForTask(task *Task) string {
+	return fmt.Sprintf("%s:%d", task.Host, task.Ports[0])
+}
+
+func isValidApp(app *App) bool {
+	if app.RunningTasks > 0 {
+		_, ok := app.Labels["prometheus"]
+		return ok
+	}
+	return false
+}
+
+func targetGroupName(app *App) string {
+	return fmt.Sprintf("marathon:%s", sanitizeName(app.ID))
+}
+
+func sanitizeName(id string) string {
+	trimID := strings.TrimLeft(id, " -/.")
+	return strings.Replace(trimID, "/", "-", -1)
+}
diff --git a/retrieval/discovery/marathon/objects.go b/retrieval/discovery/marathon/objects.go
new file mode 100644
index 000000000..7da743a51
--- /dev/null
+++ b/retrieval/discovery/marathon/objects.go
@@ -0,0 +1,32 @@
+package marathon
+
+// Task describes one instance of a service running on Marathon.
+type Task struct {
+	ID    string   `json:"id"`
+	Host  string   `json:"host"`
+	Ports []uint32 `json:"ports"`
+}
+
+// DockerContainer describes a container which uses the docker runtime.
+type DockerContainer struct {
+	Image string `json:"image"`
+}
+
+// Container describes the runtime an app in running in.
+type Container struct {
+	Docker DockerContainer `json:"docker"`
+}
+
+// App describes a service running on Marathon.
+type App struct {
+	ID           string            `json:"id"`
+	Tasks        []Task            `json:"tasks"`
+	RunningTasks int               `json:"tasksRunning"`
+	Labels       map[string]string `json:"labels"`
+	Container    Container         `json:"container"`
+}
+
+// AppList is a list of Marathon apps.
+type AppList struct {
+	Apps []App `json:"apps"`
+}
diff --git a/retrieval/discovery/marathon/url.go b/retrieval/discovery/marathon/url.go
new file mode 100644
index 000000000..61f5041f9
--- /dev/null
+++ b/retrieval/discovery/marathon/url.go
@@ -0,0 +1,15 @@
+package marathon
+
+import (
+	"fmt"
+	"math/rand"
+)
+
+const appListPath string = "/v2/apps/?embed=apps.tasks"
+
+// RandomAppsURL randomly selects a server from an array and creates an URL pointing to the app list.
+func RandomAppsURL(servers []string) string {
+	// TODO If possible update server list from Marathon at some point
+	server := servers[rand.Intn(len(servers))]
+	return fmt.Sprintf("%s%s", server, appListPath)
+}
diff --git a/retrieval/discovery/marathon_test.go b/retrieval/discovery/marathon_test.go
new file mode 100644
index 000000000..7cf6b74b6
--- /dev/null
+++ b/retrieval/discovery/marathon_test.go
@@ -0,0 +1,200 @@
+package discovery
+
+import (
+	"errors"
+	"testing"
+	"time"
+
+	clientmodel "github.com/prometheus/client_golang/model"
+
+	"github.com/prometheus/prometheus/config"
+	"github.com/prometheus/prometheus/retrieval/discovery/marathon"
+)
+
+var marathonValidLabel = map[string]string{"prometheus": "yes"}
+
+func newTestDiscovery(client marathon.AppListClient) (chan *config.TargetGroup, *MarathonDiscovery) {
+	ch := make(chan *config.TargetGroup)
+	md := NewMarathonDiscovery(&config.MarathonSDConfig{
+		Servers: []string{"http://localhost:8080"},
+	})
+	md.client = client
+	return ch, md
+}
+
+func TestMarathonSDHandleError(t *testing.T) {
+	var errTesting = errors.New("testing failure")
+	ch, md := newTestDiscovery(func(url string) (*marathon.AppList, error) {
+		return nil, errTesting
+	})
+	go func() {
+		select {
+		case tg := <-ch:
+			t.Fatalf("Got group: %s", tg)
+		default:
+		}
+	}()
+	err := md.updateServices(ch)
+	if err != errTesting {
+		t.Fatalf("Expected error: %s", err)
+	}
+}
+
+func TestMarathonSDEmptyList(t *testing.T) {
+	ch, md := newTestDiscovery(func(url string) (*marathon.AppList, error) {
+		return &marathon.AppList{}, nil
+	})
+	go func() {
+		select {
+		case tg := <-ch:
+			t.Fatalf("Got group: %v", tg)
+		default:
+		}
+	}()
+	err := md.updateServices(ch)
+	if err != nil {
+		t.Fatalf("Got error: %s", err)
+	}
+}
+
+func marathonTestAppList(labels map[string]string, runningTasks int) *marathon.AppList {
+	task := marathon.Task{
+		ID:    "test-task-1",
+		Host:  "mesos-slave1",
+		Ports: []uint32{31000},
+	}
+	docker := marathon.DockerContainer{Image: "repo/image:tag"}
+	container := marathon.Container{Docker: docker}
+	app := marathon.App{
+		ID:           "test-service",
+		Tasks:        []marathon.Task{task},
+		RunningTasks: runningTasks,
+		Labels:       labels,
+		Container:    container,
+	}
+	return &marathon.AppList{
+		Apps: []marathon.App{app},
+	}
+}
+
+func TestMarathonSDSendGroup(t *testing.T) {
+	ch, md := newTestDiscovery(func(url string) (*marathon.AppList, error) {
+		return marathonTestAppList(marathonValidLabel, 1), nil
+	})
+	go func() {
+		select {
+		case tg := <-ch:
+			if tg.Source != "marathon:test-service" {
+				t.Fatalf("Wrong target group name: %s", tg.Source)
+			}
+			if len(tg.Targets) != 1 {
+				t.Fatalf("Wrong number of targets: %v", tg.Targets)
+			}
+			tgt := tg.Targets[0]
+			if tgt[clientmodel.AddressLabel] != "mesos-slave1:31000" {
+				t.Fatalf("Wrong target address: %s", tgt[clientmodel.AddressLabel])
+			}
+		default:
+			t.Fatal("Did not get a target group.")
+		}
+	}()
+	err := md.updateServices(ch)
+	if err != nil {
+		t.Fatalf("Got error: %s", err)
+	}
+}
+
+func TestMarathonSDNoLabel(t *testing.T) {
+	ch, md := newTestDiscovery(func(url string) (*marathon.AppList, error) {
+		return marathonTestAppList(map[string]string{}, 1), nil
+	})
+	go func() {
+		select {
+		case tg := <-ch:
+			t.Fatalf("Got group: %s", tg)
+		default:
+		}
+	}()
+	err := md.updateServices(ch)
+	if err != nil {
+		t.Fatalf("Got error: %s", err)
+	}
+}
+
+func TestMarathonSDNotRunning(t *testing.T) {
+	ch, md := newTestDiscovery(func(url string) (*marathon.AppList, error) {
+		return marathonTestAppList(marathonValidLabel, 0), nil
+	})
+	go func() {
+		select {
+		case tg := <-ch:
+			t.Fatalf("Got group: %s", tg)
+		default:
+		}
+	}()
+	err := md.updateServices(ch)
+	if err != nil {
+		t.Fatalf("Got error: %s", err)
+	}
+}
+
+func TestMarathonSDRemoveApp(t *testing.T) {
+	ch, md := newTestDiscovery(func(url string) (*marathon.AppList, error) {
+		return marathonTestAppList(marathonValidLabel, 1), nil
+	})
+	go func() {
+		up1 := <-ch
+		up2 := <-ch
+		if up2.Source != up1.Source {
+			t.Fatalf("Source is different: %s", up2)
+			if len(up2.Targets) > 0 {
+				t.Fatalf("Got a non-empty target set: %s", up2.Targets)
+			}
+		}
+	}()
+	err := md.updateServices(ch)
+	if err != nil {
+		t.Fatalf("Got error on first update: %s", err)
+	}
+
+	md.client = func(url string) (*marathon.AppList, error) {
+		return marathonTestAppList(marathonValidLabel, 0), nil
+	}
+	err = md.updateServices(ch)
+	if err != nil {
+		t.Fatalf("Got error on second update: %s", err)
+	}
+}
+
+func TestMarathonSDSources(t *testing.T) {
+	_, md := newTestDiscovery(func(url string) (*marathon.AppList, error) {
+		return marathonTestAppList(marathonValidLabel, 1), nil
+	})
+	sources := md.Sources()
+	if len(sources) != 1 {
+		t.Fatalf("Wrong number of sources: %s", sources)
+	}
+}
+
+func TestMarathonSDRunAndStop(t *testing.T) {
+	ch, md := newTestDiscovery(func(url string) (*marathon.AppList, error) {
+		return marathonTestAppList(marathonValidLabel, 1), nil
+	})
+	md.refreshInterval = time.Millisecond * 10
+
+	go func() {
+		select {
+		case <-ch:
+			md.Stop()
+		case <-time.After(md.refreshInterval * 3):
+			md.Stop()
+			t.Fatalf("Update took too long.")
+		}
+	}()
+	md.Run(ch)
+	select {
+	case <-ch:
+	default:
+		t.Fatalf("Channel not closed.")
+	}
+}
diff --git a/retrieval/targetmanager.go b/retrieval/targetmanager.go
index dfb3de2b9..b0f2fd883 100644
--- a/retrieval/targetmanager.go
+++ b/retrieval/targetmanager.go
@@ -392,6 +392,9 @@ func ProvidersFromConfig(cfg *config.ScrapeConfig) []TargetProvider {
 	for _, c := range cfg.ServersetSDConfigs {
 		providers = append(providers, discovery.NewServersetDiscovery(c))
 	}
+	for _, c := range cfg.MarathonSDConfigs {
+		providers = append(providers, discovery.NewMarathonDiscovery(c))
+	}
 	if len(cfg.TargetGroups) > 0 {
 		providers = append(providers, NewStaticProvider(cfg.TargetGroups))
 	}