diff --git a/docs/source/solving.rst b/docs/source/solving.rst
index 32b7fc523..ed50da098 100644
--- a/docs/source/solving.rst
+++ b/docs/source/solving.rst
@@ -399,7 +399,7 @@ directions, all aimed at large scale problems.
    Gradient method to non-linear functions. The generalization can be
    performed in a number of different ways, resulting in a variety of
    search directions. Ceres Solver currently supports
-   ``FLETCHER_REEVES``, ``POLAK_RIBIRERE`` and ``HESTENES_STIEFEL``
+   ``FLETCHER_REEVES``, ``POLAK_RIBIERE`` and ``HESTENES_STIEFEL``
    directions.
 
 3. ``BFGS`` A generalization of the Secant method to multiple
@@ -828,7 +828,7 @@ elimination group [LiSaad]_.
 
    Default: ``FLETCHER_REEVES``
 
-   Choices are ``FLETCHER_REEVES``, ``POLAK_RIBIRERE`` and
+   Choices are ``FLETCHER_REEVES``, ``POLAK_RIBIERE`` and
    ``HESTENES_STIEFEL``.
 
 .. member:: int Solver::Options::max_lbfs_rank
diff --git a/include/ceres/types.h b/include/ceres/types.h
index 9e9124655..158e05962 100644
--- a/include/ceres/types.h
+++ b/include/ceres/types.h
@@ -247,7 +247,7 @@ enum LineSearchDirectionType {
 // details see Numerical Optimization by Nocedal & Wright.
 enum NonlinearConjugateGradientType {
   FLETCHER_REEVES,
-  POLAK_RIBIRERE,
+  POLAK_RIBIERE,
   HESTENES_STIEFEL,
 };
 
diff --git a/internal/ceres/line_search_direction.cc b/internal/ceres/line_search_direction.cc
index e04c65b63..dddcecdb1 100644
--- a/internal/ceres/line_search_direction.cc
+++ b/internal/ceres/line_search_direction.cc
@@ -65,7 +65,7 @@ class NonlinearConjugateGradient : public LineSearchDirection {
       case FLETCHER_REEVES:
         beta = current.gradient_squared_norm / previous.gradient_squared_norm;
         break;
-      case POLAK_RIBIRERE:
+      case POLAK_RIBIERE:
         gradient_change = current.gradient - previous.gradient;
         beta = (current.gradient.dot(gradient_change) /
                 previous.gradient_squared_norm);
diff --git a/internal/ceres/types.cc b/internal/ceres/types.cc
index 5a344ea43..8eaadc3e1 100644
--- a/internal/ceres/types.cc
+++ b/internal/ceres/types.cc
@@ -240,7 +240,7 @@ const char* NonlinearConjugateGradientTypeToString(
     NonlinearConjugateGradientType type) {
   switch (type) {
     CASESTR(FLETCHER_REEVES);
-    CASESTR(POLAK_RIBIRERE);
+    CASESTR(POLAK_RIBIERE);
     CASESTR(HESTENES_STIEFEL);
     default:
       return "UNKNOWN";
@@ -252,7 +252,7 @@ bool StringToNonlinearConjugateGradientType(
     NonlinearConjugateGradientType* type) {
   UpperCase(&value);
   STRENUM(FLETCHER_REEVES);
-  STRENUM(POLAK_RIBIRERE);
+  STRENUM(POLAK_RIBIERE);
   STRENUM(HESTENES_STIEFEL);
   return false;
 }