diff --git a/include/cantera/thermo/WaterSSTP.h b/include/cantera/thermo/WaterSSTP.h
index 66f4feda7..156081581 100644
--- a/include/cantera/thermo/WaterSSTP.h
+++ b/include/cantera/thermo/WaterSSTP.h
@@ -20,7 +20,7 @@ namespace Cantera
 class WaterPropsIAPWS;
 class WaterProps;
 //! Class for single-component water. This is designed to cover just the liquid
-//! part of water.
+//! and supercritical phases of water.
 /*!
  * The reference is W. Wagner, A. Pruss, "The IAPWS Formulation 1995 for the
  * Thermodynamic Properties of Ordinary Water Substance for General and
@@ -143,6 +143,8 @@ public:
         return "Water";
     }
 
+    virtual std::string phaseOfMatter() const;
+
     //! @name  Molar Thermodynamic Properties of the Solution
     //! @{
 
@@ -281,8 +283,8 @@ private:
     bool m_ready;
 
     /**
-     *  Since this phase represents a liquid phase, it's an error to
-     *  return a gas-phase answer. However, if the below is true, then
+     *  Since this phase represents a liquid (or supercritical) phase, it is an
+     *  error to return a gas-phase answer. However, if the below is true, then
      *  a gas-phase answer is allowed. This is used to check the thermodynamic
      *  consistency with ideal-gas thermo functions for example.
      */
diff --git a/interfaces/cython/cantera/test/test_purefluid.py b/interfaces/cython/cantera/test/test_purefluid.py
index 271efe62b..2dc44a617 100644
--- a/interfaces/cython/cantera/test/test_purefluid.py
+++ b/interfaces/cython/cantera/test/test_purefluid.py
@@ -367,9 +367,11 @@ class TestPureFluid(utilities.CanteraTest):
         # density before updating pressure)
         w.TP = 300, ct.one_atm
         dens = w.density
-        w.TP = 2000, ct.one_atm # supercricial
+        w.TP = 2000, ct.one_atm # supercritical
+        self.assertEqual(w.phase_of_matter, "supercritical")
         w.TP = 300, ct.one_atm # state goes from supercritical -> gas -> liquid
         self.assertNear(w.density, dens)
+        self.assertEqual(w.phase_of_matter, "liquid")
 
         # test setters for critical conditions
         w.TP = w.critical_temperature, w.critical_pressure
@@ -377,6 +379,9 @@ class TestPureFluid(utilities.CanteraTest):
         w.TP = 2000, ct.one_atm # uses current density as initial guess
         w.TP = 273.16, ct.one_atm # uses fixed density as initial guess
         self.assertNear(w.density, 999.84376)
+        self.assertEqual(w.phase_of_matter, "liquid")
+        w.TP = w.T, w.P_sat
+        self.assertEqual(w.phase_of_matter, "liquid")
         with self.assertRaisesRegex(ct.CanteraError, "violates model assumptions"):
             w.TP = 273.1599999, ct.one_atm
         with self.assertRaisesRegex(ct.CanteraError, "violates model assumptions"):
diff --git a/src/thermo/WaterSSTP.cpp b/src/thermo/WaterSSTP.cpp
index 8d37e28d3..abbea3d8e 100644
--- a/src/thermo/WaterSSTP.cpp
+++ b/src/thermo/WaterSSTP.cpp
@@ -44,6 +44,13 @@ WaterSSTP::WaterSSTP(XML_Node& phaseRoot, const std::string& id) :
     importPhase(phaseRoot, this);
 }
 
+std::string WaterSSTP::phaseOfMatter() const {
+    const vector<std::string> phases = {
+        "gas", "liquid", "supercritical", "unstable-liquid", "unstable-gas"
+    };
+    return phases[m_sub.phaseState()];
+}
+
 void WaterSSTP::initThermo()
 {
     SingleSpeciesTP::initThermo();