diff --git a/poincare/Makefile b/poincare/Makefile
index 759e538ad..aec11f95f 100644
--- a/poincare/Makefile
+++ b/poincare/Makefile
@@ -24,6 +24,7 @@ objs += $(addprefix poincare/src/,\
   matrix.o\
   matrix_data.o\
   multiplication.o\
+  naperian_logarithm.o\
   n_context.o\
   nth_root.o\
   opposite.o\
diff --git a/poincare/include/poincare.h b/poincare/include/poincare.h
index 5ee726d56..387efde16 100644
--- a/poincare/include/poincare.h
+++ b/poincare/include/poincare.h
@@ -19,6 +19,7 @@
 #include <poincare/matrix.h>
 #include <poincare/matrix_data.h>
 #include <poincare/multiplication.h>
+#include <poincare/naperian_logarithm.h>
 #include <poincare/n_context.h>
 #include <poincare/nth_root.h>
 #include <poincare/opposite.h>
diff --git a/poincare/include/poincare/expression.h b/poincare/include/poincare/expression.h
index 190400e78..238fbabab 100644
--- a/poincare/include/poincare/expression.h
+++ b/poincare/include/poincare/expression.h
@@ -20,6 +20,7 @@ class Expression {
       Logarithm,
       Matrix,
       Multiplication,
+      NaperianLogarithm,
       NthRoot,
       Opposite,
       Fraction,
diff --git a/poincare/include/poincare/naperian_logarithm.h b/poincare/include/poincare/naperian_logarithm.h
new file mode 100644
index 000000000..34bb9bef2
--- /dev/null
+++ b/poincare/include/poincare/naperian_logarithm.h
@@ -0,0 +1,15 @@
+#ifndef POINCARE_NAPERIAN_LOGARITHM_H
+#define POINCARE_NAPERIAN_LOGARITHM_H
+
+#include <poincare/function.h>
+
+class NaperianLogarithm : public Function {
+public:
+  NaperianLogarithm();
+  float approximate(Context & context) const override;
+  Type type() const override;
+  Expression * cloneWithDifferentOperands(Expression ** newOperands,
+      int numberOfOperands, bool cloneOperands = true) const override;
+};
+
+#endif
diff --git a/poincare/src/expression_lexer.l b/poincare/src/expression_lexer.l
index ad94d0ad4..008d34968 100644
--- a/poincare/src/expression_lexer.l
+++ b/poincare/src/expression_lexer.l
@@ -88,6 +88,7 @@ cos { poincare_expression_yylval.expression = new Cosine(); return FUNCTION; }
 int { poincare_expression_yylval.expression = new Integral(); return FUNCTION; }
 tan { poincare_expression_yylval.expression = new Tangent(); return FUNCTION; }
 log { poincare_expression_yylval.expression = new Logarithm(); return FUNCTION; }
+ln { poincare_expression_yylval.expression = new NaperianLogarithm(); return FUNCTION; }
 root { poincare_expression_yylval.expression = new NthRoot(); return FUNCTION; }
 sum { poincare_expression_yylval.expression = new Sum(); return FUNCTION; }
 product { poincare_expression_yylval.expression = new Product(); return FUNCTION; }
diff --git a/poincare/src/naperian_logarithm.cpp b/poincare/src/naperian_logarithm.cpp
new file mode 100644
index 000000000..632df69c4
--- /dev/null
+++ b/poincare/src/naperian_logarithm.cpp
@@ -0,0 +1,31 @@
+#include <poincare/naperian_logarithm.h>
+extern "C" {
+#include <assert.h>
+#include <math.h>
+#include <stdlib.h>
+}
+#include "layout/horizontal_layout.h"
+#include "layout/parenthesis_layout.h"
+#include "layout/string_layout.h"
+
+NaperianLogarithm::NaperianLogarithm() :
+  Function("ln")
+{
+}
+
+Expression::Type NaperianLogarithm::type() const {
+  return Type::NaperianLogarithm;
+}
+
+Expression * NaperianLogarithm::cloneWithDifferentOperands(Expression** newOperands,
+        int numberOfOperands, bool cloneOperands) const {
+  assert(numberOfOperands == 1 || numberOfOperands == 2);
+  assert(newOperands != nullptr);
+  NaperianLogarithm * l = new NaperianLogarithm();
+  l->setArgument(newOperands, numberOfOperands, cloneOperands);
+  return l;
+}
+
+float NaperianLogarithm::approximate(Context& context) const {
+  return log10f(m_args[0]->approximate(context))/log10f(M_E);
+}