diff --git a/homeassistant/components/smarttub/__init__.py b/homeassistant/components/smarttub/__init__.py
index 8467c208076..457af4b7bc0 100644
--- a/homeassistant/components/smarttub/__init__.py
+++ b/homeassistant/components/smarttub/__init__.py
@@ -7,7 +7,7 @@ from .controller import SmartTubController
 
 _LOGGER = logging.getLogger(__name__)
 
-PLATFORMS = ["climate", "light", "sensor", "switch"]
+PLATFORMS = ["binary_sensor", "climate", "light", "sensor", "switch"]
 
 
 async def async_setup(hass, config):
diff --git a/homeassistant/components/smarttub/binary_sensor.py b/homeassistant/components/smarttub/binary_sensor.py
new file mode 100644
index 00000000000..52dbfd71a37
--- /dev/null
+++ b/homeassistant/components/smarttub/binary_sensor.py
@@ -0,0 +1,40 @@
+"""Platform for binary sensor integration."""
+import logging
+
+from homeassistant.components.binary_sensor import (
+    DEVICE_CLASS_CONNECTIVITY,
+    BinarySensorEntity,
+)
+
+from .const import DOMAIN, SMARTTUB_CONTROLLER
+from .entity import SmartTubSensorBase
+
+_LOGGER = logging.getLogger(__name__)
+
+
+async def async_setup_entry(hass, entry, async_add_entities):
+    """Set up binary sensor entities for the binary sensors in the tub."""
+
+    controller = hass.data[DOMAIN][entry.entry_id][SMARTTUB_CONTROLLER]
+
+    entities = [SmartTubOnline(controller.coordinator, spa) for spa in controller.spas]
+
+    async_add_entities(entities)
+
+
+class SmartTubOnline(SmartTubSensorBase, BinarySensorEntity):
+    """A binary sensor indicating whether the spa is currently online (connected to the cloud)."""
+
+    def __init__(self, coordinator, spa):
+        """Initialize the entity."""
+        super().__init__(coordinator, spa, "Online", "online")
+
+    @property
+    def is_on(self) -> bool:
+        """Return true if the binary sensor is on."""
+        return self._state is True
+
+    @property
+    def device_class(self) -> str:
+        """Return the device class for this entity."""
+        return DEVICE_CLASS_CONNECTIVITY
diff --git a/homeassistant/components/smarttub/entity.py b/homeassistant/components/smarttub/entity.py
index eab60b4162c..8be956a2b70 100644
--- a/homeassistant/components/smarttub/entity.py
+++ b/homeassistant/components/smarttub/entity.py
@@ -13,8 +13,6 @@ from .helpers import get_spa_name
 
 _LOGGER = logging.getLogger(__name__)
 
-PLATFORMS = ["climate"]
-
 
 class SmartTubEntity(CoordinatorEntity):
     """Base class for SmartTub entities."""
@@ -57,3 +55,17 @@ class SmartTubEntity(CoordinatorEntity):
         """Retrieve the result of Spa.get_status()."""
 
         return self.coordinator.data[self.spa.id].get("status")
+
+
+class SmartTubSensorBase(SmartTubEntity):
+    """Base class for SmartTub sensors."""
+
+    def __init__(self, coordinator, spa, sensor_name, attr_name):
+        """Initialize the entity."""
+        super().__init__(coordinator, spa, sensor_name)
+        self._attr_name = attr_name
+
+    @property
+    def _state(self):
+        """Retrieve the underlying state from the spa."""
+        return getattr(self.spa_status, self._attr_name)
diff --git a/homeassistant/components/smarttub/sensor.py b/homeassistant/components/smarttub/sensor.py
index 4619d07dbe0..be3d60c0241 100644
--- a/homeassistant/components/smarttub/sensor.py
+++ b/homeassistant/components/smarttub/sensor.py
@@ -3,7 +3,7 @@ from enum import Enum
 import logging
 
 from .const import DOMAIN, SMARTTUB_CONTROLLER
-from .entity import SmartTubEntity
+from .entity import SmartTubSensorBase
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -42,18 +42,8 @@ async def async_setup_entry(hass, entry, async_add_entities):
     async_add_entities(entities)
 
 
-class SmartTubSensor(SmartTubEntity):
-    """Generic and base class for SmartTub sensors."""
-
-    def __init__(self, coordinator, spa, sensor_name, attr_name):
-        """Initialize the entity."""
-        super().__init__(coordinator, spa, sensor_name)
-        self._attr_name = attr_name
-
-    @property
-    def _state(self):
-        """Retrieve the underlying state from the spa."""
-        return getattr(self.spa_status, self._attr_name)
+class SmartTubSensor(SmartTubSensorBase):
+    """Generic class for SmartTub status sensors."""
 
     @property
     def state(self) -> str:
diff --git a/tests/components/smarttub/conftest.py b/tests/components/smarttub/conftest.py
index 79e5d06d3b3..b7c90b5ad3e 100644
--- a/tests/components/smarttub/conftest.py
+++ b/tests/components/smarttub/conftest.py
@@ -48,6 +48,7 @@ def mock_spa():
             "setTemperature": 39,
             "water": {"temperature": 38},
             "heater": "ON",
+            "online": True,
             "heatMode": "AUTO",
             "state": "NORMAL",
             "primaryFiltration": {
diff --git a/tests/components/smarttub/test_binary_sensor.py b/tests/components/smarttub/test_binary_sensor.py
new file mode 100644
index 00000000000..b2624369e96
--- /dev/null
+++ b/tests/components/smarttub/test_binary_sensor.py
@@ -0,0 +1,13 @@
+"""Test the SmartTub binary sensor platform."""
+
+from homeassistant.components.binary_sensor import DEVICE_CLASS_CONNECTIVITY, STATE_ON
+
+
+async def test_binary_sensors(spa, setup_entry, hass):
+    """Test the binary sensors."""
+
+    entity_id = f"binary_sensor.{spa.brand}_{spa.model}_online"
+    state = hass.states.get(entity_id)
+    assert state is not None
+    assert state.state == STATE_ON
+    assert state.attributes.get("device_class") == DEVICE_CLASS_CONNECTIVITY