diff --git a/Triangulation_on_sphere_2/include/CGAL/Delaunay_triangulation_on_sphere_2.h b/Triangulation_on_sphere_2/include/CGAL/Delaunay_triangulation_on_sphere_2.h
index cfa30343a96..9012a72b79c 100644
--- a/Triangulation_on_sphere_2/include/CGAL/Delaunay_triangulation_on_sphere_2.h
+++ b/Triangulation_on_sphere_2/include/CGAL/Delaunay_triangulation_on_sphere_2.h
@@ -19,6 +19,7 @@
 #include <CGAL/Triangulation_on_sphere_2.h>
 #include <CGAL/Triangulation_on_sphere_face_base_2.h>
 #include <CGAL/Triangulation_on_sphere_vertex_base_2.h>
+#include <CGAL/Triangulation_on_sphere_2/IO/OFF.h>
 
 #include <CGAL/enum.h>
 #include <CGAL/Origin.h>
diff --git a/Triangulation_on_sphere_2/include/CGAL/Triangulation_on_sphere_2/IO/OFF.h b/Triangulation_on_sphere_2/include/CGAL/Triangulation_on_sphere_2/IO/OFF.h
new file mode 100644
index 00000000000..082ff3ab5f2
--- /dev/null
+++ b/Triangulation_on_sphere_2/include/CGAL/Triangulation_on_sphere_2/IO/OFF.h
@@ -0,0 +1,173 @@
+// Copyright (c) 2021 GeometryFactory (France).  All rights reserved.
+//
+// This file is part of CGAL (www.cgal.org)
+//
+// $URL$
+// $Id$
+// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
+//
+// Author(s)     : Mael Rouxel-Labbé
+
+#ifndef CGAL_TOS2_IO_OFF_H
+#define CGAL_TOS2_IO_OFF_H
+
+#include <CGAL/license/Triangulation_on_sphere_2.h>
+
+#include <CGAL/boost/graph/Named_function_parameters.h>
+#include <CGAL/boost/graph/named_params_helper.h>
+#include <CGAL/IO/helpers.h>
+#include <CGAL/IO/read_off_points.h>
+#include <CGAL/IO/write_off_points.h>
+
+#include <fstream>
+#include <string>
+
+#ifdef DOXYGEN_RUNNING
+#define CGAL_BGL_NP_TEMPLATE_PARAMETERS NamedParameters
+#define CGAL_BGL_NP_CLASS NamedParameters
+#define CGAL_DEPRECATED
+#endif
+
+namespace CGAL {
+
+template <typename Gt, typename Tds>
+class Delaunay_triangulation_on_sphere_2;
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// Read
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// Write
+
+/*!
+  \ingroup PkgPointSet3IOOFF
+
+  \brief writes the content of a triangulation on the sphere into an output stream in the \ref IOStreamOFF.
+
+  \tparam Gt the geometric traits type of the triangulation
+  \tparam Tds the triangulation data structure type of the triangulation
+  \tparam NamedParameters a sequence of \ref bgl_namedparameters "Named Parameters"
+
+  \param os the output stream
+  \param dt the triangulation
+  \param np an optional sequence of \ref bgl_namedparameters "Named Parameters" among the ones listed below
+
+  \cgalNamedParamsBegin
+    \cgalParamNBegin{stream_precision}
+      \cgalParamDescription{a parameter used to set the precision (i.e. how many digits are generated) of the output stream}
+      \cgalParamType{int}
+      \cgalParamDefault{the precision of the stream `os`}
+    \cgalParamNEnd
+  \cgalNamedParamsEnd
+
+  \return `true` if the writing was successful, `false` otherwise.
+ */
+template <typename Gt, typename Tds, typename CGAL_BGL_NP_TEMPLATE_PARAMETERS>
+bool write_OFF(std::ostream& os,
+               const CGAL::Delaunay_triangulation_on_sphere_2<Gt, Tds>& dt,
+               const CGAL_BGL_NP_CLASS& np)
+{
+  typedef Delaunay_triangulation_on_sphere_2<Gt,Tds>    Tr;
+  typedef typename Tr::Vertex_handle                    Vertex_handle;
+  typedef typename Tr::All_vertices_iterator            Vertex_iterator;
+  typedef typename Tr::All_faces_iterator               Face_iterator;
+
+  typename Gt::Construct_point_3 cp3 = dt.geom_traits().construct_point_3_object();
+
+  const size_t n = dt.number_of_vertices();
+
+  std::stringstream output;
+
+  // write the vertices
+  std::unordered_map<Vertex_handle, int> index_of_vertex;
+  int i = 0;
+  for(Vertex_iterator it = dt.vertices_begin(); it != dt.vertices_end(); ++it, ++i)
+  {
+    Vertex_handle vh = it;
+    output << cp3(vh->point()) << " 0 0 0 \n"; // '0 0 0' for colors
+    index_of_vertex[vh] = i;
+  }
+
+  CGAL_assertion( i == n );
+
+  size_t number_of_triangles = 0;
+
+  for (Face_iterator fit = dt.all_faces_begin() ; fit != dt.all_faces_end() ; ++fit)
+  {
+    output << "3 "
+           << index_of_vertex[fit->vertex(0)] << " "
+           << index_of_vertex[fit->vertex(1)] << " "
+           << index_of_vertex[fit->vertex(2)]
+           << " ";
+    if(fit->is_ghost())
+      output << " 229 117 0\n";
+    else
+      output << " 0 117 229\n";
+
+    ++number_of_triangles;
+  }
+
+  os << "COFF \n"
+     << n << " "
+     << number_of_triangles << " 0\n"
+     << output.str();
+
+  return !os.fail();
+}
+
+/// \cond SKIP_IN_MANUAL
+
+template <typename Gt, typename Tds>
+bool write_OFF(std::ostream& os, const CGAL::Delaunay_triangulation_on_sphere_2<Gt, Tds>& dt)
+{
+  return write_OFF(os, dt, parameters::all_default());
+}
+
+/// \endcond
+
+/*!
+  \ingroup PkgPointSet3IOOFF
+
+  \brief writes the content of a triangulation on the sphere into an output file in the \ref IOStreamOFF.
+
+  \tparam Gt the geometric traits type of the triangulation
+  \tparam Tds the triangulation data structure type of the triangulation
+  \tparam NamedParameters a sequence of \ref bgl_namedparameters "Named Parameters"
+
+  \param fname the path to the output file
+  \param point_set the point set
+  \param np an optional sequence of \ref bgl_namedparameters "Named Parameters" among the ones listed below
+
+  \cgalNamedParamsBegin
+    \cgalParamNBegin{stream_precision}
+      \cgalParamDescription{a parameter used to set the precision (i.e. how many digits are generated) of the output stream}
+      \cgalParamType{int}
+      \cgalParamDefault{`6`}
+    \cgalParamNEnd
+  \cgalNamedParamsEnd
+
+  \return `true` if the writing was successful, `false` otherwise.
+*/
+template <typename Gt, typename Tds, typename CGAL_BGL_NP_TEMPLATE_PARAMETERS>
+bool write_OFF(const std::string& fname, const CGAL::Delaunay_triangulation_on_sphere_2<Gt, Tds>& dt, const CGAL_BGL_NP_CLASS& np)
+{
+  std::ofstream os(fname);
+  return write_OFF(os, dt, np);
+}
+
+/// \cond SKIP_IN_MANUAL
+
+template <typename Gt, typename Tds>
+bool write_OFF(const std::string& fname, const CGAL::Delaunay_triangulation_on_sphere_2<Gt, Tds>& dt)
+{
+  std::ofstream os(fname);
+  return write_OFF(os, dt, parameters::all_default());
+}
+
+/// \endcond
+
+} // namespace CGAL
+
+#endif // CGAL_TOS2_IO_OFF_H