diff --git a/include/cantera/thermo/Phase.h b/include/cantera/thermo/Phase.h
index 8a8009e49..dddc81e11 100644
--- a/include/cantera/thermo/Phase.h
+++ b/include/cantera/thermo/Phase.h
@@ -781,6 +781,9 @@ public:
     //! Return the Species object for the named species.
     shared_ptr<Species> species(const std::string& name) const;
 
+    //! Return the Species object for species whose index is *k*.
+    shared_ptr<Species> species(size_t k) const;
+
     //! Set behavior when adding a species containing undefined elements to just
     //! skip the species.
     void ignoreUndefinedElements();
diff --git a/src/thermo/Phase.cpp b/src/thermo/Phase.cpp
index 7379d5974..4486f7bdc 100644
--- a/src/thermo/Phase.cpp
+++ b/src/thermo/Phase.cpp
@@ -971,6 +971,11 @@ shared_ptr<Species> Phase::species(const std::string& name) const
     return getValue(m_species, name);
 }
 
+shared_ptr<Species> Phase::species(size_t k) const
+{
+    return species(m_speciesNames[k]);
+}
+
 void Phase::ignoreUndefinedElements() {
     m_undefinedElementBehavior = UndefElement::ignore;
 }