diff --git a/include/cantera/thermo/Phase.h b/include/cantera/thermo/Phase.h
index 0dc75d7f4..5365a3b41 100644
--- a/include/cantera/thermo/Phase.h
+++ b/include/cantera/thermo/Phase.h
@@ -124,30 +124,31 @@ public:
      */
     void setXMLdata(XML_Node& xmlPhase);
 
-    /*! @name Name and ID
-     * Class Phase contains two strings that identify a phase. The ID is the
-     * value of the ID attribute of the XML phase node that is used to
-     * initialize a phase when it is read. The name field is also initialized
-     * to the value of the ID attribute of the XML phase node.
+    /*! @name Name
+     * Class Phase uses the string name to identify a phase. The name is the
+     * value of the corresponding key in the phase map (in YAML), name (in
+     * CTI), or id (in XML) that is used to initialize a phase when it is read.
      *
      * However, the name field may be changed to another value during the
-     * course of a calculation. For example, if a phase is located in two
-     * places, but has the same constitutive input, the IDs of the two phases
-     * will be the same, but the names of the two phases may be different.
-     *
-     * It is an error to have two phases in a single problem with the same name
-     * and ID (or the name from one phase being the same as the id of
-     * another phase). Thus, it is expected that there is a 1-1 correspondence
-     * between names and unique phases within a Cantera problem.
+     * course of a calculation. For example, if duplicates of a phase object
+     * are instantiated and used in multiple places (e.g. a ReactorNet), they
+     * will have the same constitutive input, i.e. the names of the phases will
+     * be the same. Note that this is not a problem for Cantera internally;
+     * however, a user may want to rename phase objects in order to clarify.
      */
     //!@{
 
     //! Return the string id for the phase.
+    /*!
+     * @deprecated To be removed after Cantera 2.5.
+     */
     std::string id() const;
 
     //! Set the string id for the phase.
     /*!
      *    @param id String id of the phase
+     *
+     * @deprecated To be removed after Cantera 2.5.
      */
     void setID(const std::string& id);
 
diff --git a/interfaces/cython/cantera/composite.py b/interfaces/cython/cantera/composite.py
index 191d1d2ea..b5d661c67 100644
--- a/interfaces/cython/cantera/composite.py
+++ b/interfaces/cython/cantera/composite.py
@@ -39,8 +39,9 @@ class Solution(ThermoPhase, Kinetics, Transport):
         gas = ct.Solution('diamond.yaml', name='gas')
         diamond = ct.Solution('diamond.yaml', name='diamond')
 
-    The name of the `Solution` object defaults to the *phase* specified in the 
-    input file. Once instatiated, a custom name can assigned via::
+    The name of the `Solution` object defaults to the *phase* identifier 
+    specified in the input file. Upon initialization of a 'Solution' object, 
+    a custom name can assigned via::
 
         gas.name = 'my_custom_name'
 
diff --git a/interfaces/cython/cantera/test/test_mixture.py b/interfaces/cython/cantera/test/test_mixture.py
index b96107ee1..42f882bb4 100644
--- a/interfaces/cython/cantera/test/test_mixture.py
+++ b/interfaces/cython/cantera/test/test_mixture.py
@@ -112,11 +112,10 @@ class TestMixture(utilities.CanteraTest):
 
     def test_phase_moles(self):
         M = self.mix.phase_moles()
-        name = self.phase2.name
         self.assertEqual(M[0], self.mix.phase_moles(0))
-        self.assertEqual(M[1], self.mix.phase_moles(name))
+        self.assertEqual(M[1], self.mix.phase_moles('air'))
 
-        self.mix.set_phase_moles(name, 4)
+        self.mix.set_phase_moles('air', 4)
         self.assertEqual(self.mix.phase_moles(1), 4)
 
     def test_species_moles(self):
diff --git a/src/kinetics/Kinetics.cpp b/src/kinetics/Kinetics.cpp
index 300110b57..570f592f9 100644
--- a/src/kinetics/Kinetics.cpp
+++ b/src/kinetics/Kinetics.cpp
@@ -306,7 +306,7 @@ size_t Kinetics::kineticsSpeciesIndex(const std::string& nm,
     }
 
     for (size_t n = 0; n < m_thermo.size(); n++) {
-        string id = thermo(n).id();
+        string id = thermo(n).name();
         if (ph == id) {
             size_t k = thermo(n).speciesIndex(nm);
             if (k == npos) {
@@ -451,7 +451,7 @@ void Kinetics::addPhase(thermo_t& thermo)
         m_rxnphase = nPhases();
     }
     m_thermo.push_back(&thermo);
-    m_phaseindex[m_thermo.back()->id()] = nPhases();
+    m_phaseindex[m_thermo.back()->name()] = nPhases();
     resizeSpecies();
 }
 
@@ -608,7 +608,7 @@ shared_ptr<Reaction> Kinetics::reaction(size_t i)
     checkReactionIndex(i);
     return m_reactions[i];
 }
-    
+
 shared_ptr<const Reaction> Kinetics::reaction(size_t i) const
 {
     checkReactionIndex(i);
diff --git a/src/kinetics/importKinetics.cpp b/src/kinetics/importKinetics.cpp
index 7d05355ff..296eb6f35 100644
--- a/src/kinetics/importKinetics.cpp
+++ b/src/kinetics/importKinetics.cpp
@@ -168,7 +168,7 @@ bool importKinetics(const XML_Node& phase, std::vector<ThermoPhase*> th,
         // loop over the supplied 'ThermoPhase' objects representing
         // phases, to find an object with the same id.
         for (size_t m = 0; m < th.size(); m++) {
-            if (th[m]->id() == phase_id) {
+            if (th[m]->name() == phase_id) {
                 phase_ok = true;
                 // if no phase with this id has been added to
                 //the kinetics manager yet, then add this one
@@ -176,7 +176,7 @@ bool importKinetics(const XML_Node& phase, std::vector<ThermoPhase*> th,
                     k->addPhase(*th[m]);
                 }
             }
-            msg += " "+th[m]->id();
+            msg += " "+th[m]->name();
         }
         if (!phase_ok) {
             throw CanteraError("importKinetics",
@@ -254,7 +254,7 @@ bool checkElectrochemReaction(const XML_Node& p, Kinetics& kin, const XML_Node&
         size_t k = ph.speciesIndex(sp.first);
         double stoich = sp.second;
         for (size_t m = 0; m < phase_ids.size(); m++) {
-            if (phase_ids[m] == ph.id()) {
+            if (phase_ids[m] == ph.name()) {
                 e_counter[m] += stoich * ph.charge(k);
                 break;
             }
@@ -267,7 +267,7 @@ bool checkElectrochemReaction(const XML_Node& p, Kinetics& kin, const XML_Node&
         size_t k = ph.speciesIndex(sp.first);
         double stoich = sp.second;
         for (size_t m = 0; m < phase_ids.size(); m++) {
-            if (phase_ids[m] == ph.id()) {
+            if (phase_ids[m] == ph.name()) {
                 e_counter[m] -= stoich * ph.charge(k);
                 break;
             }
diff --git a/src/thermo/FixedChemPotSSTP.cpp b/src/thermo/FixedChemPotSSTP.cpp
index a94a0e105..62105fdf9 100644
--- a/src/thermo/FixedChemPotSSTP.cpp
+++ b/src/thermo/FixedChemPotSSTP.cpp
@@ -40,7 +40,6 @@ FixedChemPotSSTP::FixedChemPotSSTP(const std::string& Ename, doublereal val) :
     chemPot_(0.0)
 {
     std::string pname = Ename + "Fixed";
-    setID(pname);
     setName(pname);
     setNDim(3);
     addElement(Ename);
diff --git a/src/thermo/LatticeSolidPhase.cpp b/src/thermo/LatticeSolidPhase.cpp
index 02293b85b..a3ce57767 100644
--- a/src/thermo/LatticeSolidPhase.cpp
+++ b/src/thermo/LatticeSolidPhase.cpp
@@ -347,7 +347,7 @@ void LatticeSolidPhase::setLatticeStoichiometry(const compositionMap& comp)
     }
     // Add in the lattice stoichiometry constraint
     for (size_t i = 1; i < m_lattice.size(); i++) {
-        string econ = fmt::format("LC_{}_{}", i, id());
+        string econ = fmt::format("LC_{}_{}", i, name());
         size_t m = addElement(econ, 0.0, 0, 0.0, CT_ELEM_TYPE_LATTICERATIO);
         size_t mm = nElements();
         for (size_t k = 0; k < m_lattice[0]->nSpecies(); k++) {
diff --git a/src/thermo/Phase.cpp b/src/thermo/Phase.cpp
index f1ef31a9a..e662fbded 100644
--- a/src/thermo/Phase.cpp
+++ b/src/thermo/Phase.cpp
@@ -68,11 +68,17 @@ void Phase::setXMLdata(XML_Node& xmlPhase)
 
 std::string Phase::id() const
 {
+    warn_deprecated("Phase::id",
+                    "To be removed after Cantera 2.5. "
+                    "Usage merged with 'Phase::name'");
     return m_id;
 }
 
 void Phase::setID(const std::string& id_)
 {
+    warn_deprecated("Phase::setID",
+                    "To be removed after Cantera 2.5. "
+                    "Usage merged with 'Phase::setName'");
     m_id = id_;
     m_name = id_;
 }
diff --git a/src/thermo/PureFluidPhase.cpp b/src/thermo/PureFluidPhase.cpp
index 2382ac511..5b7732350 100644
--- a/src/thermo/PureFluidPhase.cpp
+++ b/src/thermo/PureFluidPhase.cpp
@@ -64,7 +64,7 @@ void PureFluidPhase::initThermo()
     m_sub->setStdState(h0_RT*GasConstant*298.15/m_mw,
                        s_R*GasConstant/m_mw, T0, p);
     debuglog("PureFluidPhase::initThermo: initialized phase "
-             +id()+"\n", m_verbose);
+             +name()+"\n", m_verbose);
 }
 
 void PureFluidPhase::setParametersFromXML(const XML_Node& eosdata)
diff --git a/src/thermo/ThermoFactory.cpp b/src/thermo/ThermoFactory.cpp
index 239c4af6a..d9e64b4aa 100644
--- a/src/thermo/ThermoFactory.cpp
+++ b/src/thermo/ThermoFactory.cpp
@@ -250,7 +250,6 @@ void importPhase(XML_Node& phase, ThermoPhase* th)
     th->setXMLdata(phase);
 
     // set the id attribute of the phase to the 'id' attribute in the XML tree.
-    th->setID(phase.id());
     th->setName(phase.id());
 
     // Number of spatial dimensions. Defaults to 3 (bulk phase)
@@ -258,7 +257,7 @@ void importPhase(XML_Node& phase, ThermoPhase* th)
         int idim = intValue(phase["dim"]);
         if (idim < 1 || idim > 3) {
             throw CanteraError("importPhase",
-                               "phase, " + th->id() +
+                               "phase, " + th->name() +
                                ", has unphysical number of dimensions: " + phase["dim"]);
         }
         th->setNDim(idim);
@@ -274,7 +273,7 @@ void importPhase(XML_Node& phase, ThermoPhase* th)
         th->setParametersFromXML(eos);
     } else {
         throw CanteraError("importPhase",
-                           " phase, " + th->id() +
+                           " phase, " + th->name() +
                            ", XML_Node does not have a \"thermo\" XML_Node");
     }
 
@@ -284,7 +283,7 @@ void importPhase(XML_Node& phase, ThermoPhase* th)
         vpss_ptr = dynamic_cast <VPStandardStateTP*>(th);
         if (vpss_ptr == 0) {
             throw CanteraError("importPhase",
-                               "phase, " + th->id() + ", was VPSS, but dynamic cast failed");
+                               "phase, " + th->name() + ", was VPSS, but dynamic cast failed");
         }
     }
 
@@ -300,7 +299,7 @@ void importPhase(XML_Node& phase, ThermoPhase* th)
     vector<XML_Node*> sparrays = phase.getChildren("speciesArray");
     if (ssConvention != cSS_CONVENTION_SLAVE && sparrays.empty()) {
         throw CanteraError("importPhase",
-                           "phase, " + th->id() + ", has zero \"speciesArray\" XML nodes.\n"
+                           "phase, " + th->name() + ", has zero \"speciesArray\" XML nodes.\n"
                            + " There must be at least one speciesArray nodes "
                            "with one or more species");
     }
@@ -448,7 +447,6 @@ void addSpecies(ThermoPhase& thermo, const AnyValue& names, const AnyValue& spec
 void setupPhase(ThermoPhase& thermo, AnyMap& phaseNode, const AnyMap& rootNode)
 {
     thermo.setName(phaseNode["name"].asString());
-    thermo.setID(phaseNode["name"].asString());
     if (rootNode.hasKey("__file__")) {
         phaseNode["__file__"] = rootNode["__file__"];
     }