diff --git a/Documentation/doc/resources/1.8.13/BaseDoxyfile.in b/Documentation/doc/resources/1.8.13/BaseDoxyfile.in
index 91112fc97809..58d604b35c9d 100644
--- a/Documentation/doc/resources/1.8.13/BaseDoxyfile.in
+++ b/Documentation/doc/resources/1.8.13/BaseDoxyfile.in
@@ -106,7 +106,6 @@ ALIASES                = "cgal=%CGAL" \
                          "taucs=TAUCS" \
                          "lapack=LAPACK" \
                          "blas=BLAS" \
-                         "opennl=OpenNL" \
                          "cpp=C++" \
                          "cpp11=C++11" \
                          "CC=C++" \
@@ -768,4 +767,3 @@ DIRECTORY_GRAPH        = NO
 # This tag requires that the tag HAVE_DOT is set to YES.
 
 INTERACTIVE_SVG        = YES
-
diff --git a/OpenNL/include/CGAL/OpenNL/linear_solver.h b/OpenNL/include/CGAL/OpenNL/linear_solver.h
deleted file mode 100644
index 47a52dfecebf..000000000000
--- a/OpenNL/include/CGAL/OpenNL/linear_solver.h
+++ /dev/null
@@ -1,291 +0,0 @@
-// Copyright (c) 2005-2008  Inria Loria (France).
-/*
- * author:  Bruno Levy, INRIA, project ALICE
- * website: https://www.loria.fr/~levy/software
- *
- * This file is part of CGAL (www.cgal.org)
- *
- * Scientific work that use this software can reference the website and
- * the following publication:
- *
- * @INPROCEEDINGS {levy:NMDGP:05,
- *    AUTHOR = Bruno Levy,
- *    TITLE  = Numerical Methods for Digital Geometry Processing,
- *    BOOKTITLE =Israel Korea Bi-National Conference,
- *    YEAR=November 2005,
- *    URL=https://www.loria.fr/~levy/php/article.php?pub=../publications/papers/2005/Numerics
- * }
- *
- *  Laurent Saboret 2005-2006: Changes for CGAL:
- *      - Added OpenNL namespace
- *      - DefaultLinearSolverTraits is now a model of the SparseLinearAlgebraTraits_d concept
- *      - Added SymmetricLinearSolverTraits
- *      - copied Jacobi preconditioner from Graphite 1.9 code
- *
- * $URL$
- * $Id$
- * SPDX-License-Identifier: LGPL-3.0-or-later
- */
-
-
-#ifndef __OPENNL_LINEAR_SOLVER__
-#define __OPENNL_LINEAR_SOLVER__
-
-#include <vector>
-#include <iostream>
-#include <cstdlib>
-
-#include <CGAL/use.h>
-
-namespace OpenNL {
-
-
-
-
-/*
- * Solves a linear system or minimizes a quadratic form.
- *
- * Requirements for its traits class: must be a model of SparseLinearSolverTraits_d concept
- */
-template <class TRAITS>
-class LinearSolver
-{
-protected:
-    enum State {
-        INITIAL, IN_SYSTEM, IN_ROW, CONSTRUCTED, SOLVED
-    } ;
-
-public:
-    typedef TRAITS Traits ;
-    typedef typename Traits::Matrix Matrix ;
-    typedef typename Traits::Vector Vector ;
-    typedef typename Traits::NT CoeffType ;
-
-    class Variable {
-    public:
-        Variable() : x_(0), index_(-1), locked_(false) { }
-        double value() const { return x_; }
-        void set_value(double x_in) { x_ = x_in ; }
-        void lock()   { locked_ = true ; }
-        void unlock() { locked_ = false ; }
-        bool is_locked() const { return locked_ ; }
-        unsigned int index() const {
-            CGAL_assertion(index_ != -1) ;
-            return (unsigned int)(index_) ;
-        }
-        void set_index(unsigned int index_in) {
-            index_ = index_in ;
-        }
-    private:
-        CoeffType x_ ;
-        int index_ ;
-        bool locked_ ;
-    }  ;
-
-
-    LinearSolver(unsigned int nb_variables) {
-        state_ = INITIAL ;
-        least_squares_ = false ;
-        nb_variables_ = nb_variables ;
-        variable_ = new Variable[nb_variables] ;
-        A_ = nullptr ;
-        x_ = nullptr ;
-        b_ = nullptr ;
-    }
-
-    ~LinearSolver() {
-        delete[] variable_ ;
-        delete A_ ;
-        delete x_ ;
-        delete b_ ;
-    }
-
-    // __________________ Parameters ________________________
-
-    void set_least_squares(bool x) { least_squares_ = x ; }
-
-    // __________________ Access ____________________________
-
-    int nb_variables() const { return nb_variables_ ; }
-
-    Variable& variable(unsigned int idx) {
-        CGAL_assertion(idx < nb_variables_) ;
-        return variable_[idx] ;
-    }
-
-    const Variable& variable(unsigned int idx) const {
-        CGAL_assertion(idx < nb_variables_) ;
-        return variable_[idx] ;
-    }
-
-    // _________________ Construction _______________________
-
-    void begin_system() {
-        current_row_ = 0 ;
-        transition(INITIAL, IN_SYSTEM) ;
-        // Enumerate free variables.
-        unsigned int index = 0 ;
-        for(int ii=0; ii < nb_variables() ; ii++) {
-            Variable& v = variable(ii) ;
-            if(!v.is_locked()) {
-                v.set_index(index) ;
-                index++ ;
-            }
-        }
-        unsigned int n = index ;
-        A_ = new Matrix(static_cast<int>(n)) ;
-        x_ = new Vector(n) ;
-        b_ = new Vector(n) ;
-        for(unsigned int i=0; i<n; i++) {
-            (*x_)[i] = 0 ;
-            (*b_)[i] = 0 ;
-        }
-        variables_to_vector() ;
-    }
-
-    void begin_row() {
-        transition(IN_SYSTEM, IN_ROW) ;
-        af_.clear() ;
-        if_.clear() ;
-        al_.clear() ;
-        xl_.clear() ;
-        bk_ = 0 ;
-    }
-
-    void add_coefficient(unsigned int iv, double a) {
-        check_state(IN_ROW) ;
-        Variable& v = variable(iv) ;
-        if(v.is_locked()) {
-            al_.push_back(a) ;
-            xl_.push_back(v.value()) ;
-        } else {
-            af_.push_back(a) ;
-            if_.push_back(v.index()) ;
-        }
-    }
-
-
-    void end_row() {
-        if(least_squares_) {
-            std::size_t nf = af_.size() ;
-            std::size_t nl = al_.size() ;
-            for(std::size_t i=0; i<nf; i++) {
-                for(std::size_t j=0; j<nf; j++) {
-                    A_->add_coef(if_[i], if_[j], af_[i] * af_[j]) ;
-                }
-            }
-            CoeffType S = - bk_ ;
-            for(std::size_t j=0; j<nl; j++) {
-                S += al_[j] * xl_[j] ;
-            }
-            for(std::size_t i=0; i<nf; i++) {
-                (*b_)[if_[i]] -= af_[i] * S ;
-            }
-        } else {
-            std::size_t nf = af_.size() ;
-            std::size_t nl = al_.size() ;
-            for(std::size_t i=0; i<nf; i++) {
-                A_->add_coef(current_row_, if_[i], af_[i]) ;
-            }
-            (*b_)[current_row_] = bk_ ;
-            for(std::size_t i=0; i<nl; i++) {
-                (*b_)[current_row_] -= al_[i] * xl_[i] ;
-            }
-        }
-        current_row_++ ;
-        transition(IN_ROW, IN_SYSTEM) ;
-    }
-
-    void end_system() {
-        transition(IN_SYSTEM, CONSTRUCTED) ;
-    }
-
-    // ----------------------------- Solver -------------------------------
-
-    // Solves a linear system or minimizes a quadratic form.
-    // Return true on success.
-    // (modified for SparseLinearAlgebraTraits_d concept)
-    bool solve()
-    {
-        check_state(CONSTRUCTED) ;
-
-        // Solve the sparse linear system "A*X = B". On success, the solution is (1/D) * X.
-        Traits solver_traits;
-        CoeffType D;
-        bool success = solver_traits.linear_solver(*A_, *b_, *x_, D) ;
-        CGAL_assertion(D == 1.0);   // WARNING: this library does not support homogeneous coordinates!
-
-        vector_to_variables() ;
-
-        transition(CONSTRUCTED, SOLVED) ;
-
-        delete A_ ; A_ = nullptr ;
-        delete b_ ; b_ = nullptr ;
-        delete x_ ; x_ = nullptr ;
-
-        return success;
-    }
-
-protected:
-
-    // ----------- Converting between user representation and the internal representation -----
-
-    void vector_to_variables() {
-        for(int ii=0; ii < nb_variables(); ii++) {
-            Variable& v = variable(ii) ;
-            if(!v.is_locked()) {
-                v.set_value( (*x_)[v.index()] ) ;
-            }
-        }
-    }
-
-    void variables_to_vector() {
-        for(int ii=0; ii < nb_variables(); ii++) {
-            Variable& v = variable(ii) ;
-            if(!v.is_locked()) {
-                (*x_)[v.index()] = v.value() ;
-            }
-        }
-    }
-
-    // ----------- Finite state automaton (checks that calling sequence is respected) ---------
-
-    void check_state(State s) {
-            CGAL_USE(s);
-            CGAL_assertion(state_ == s) ;
-    }
-
-    void transition(State from, State to) {
-            check_state(from) ;
-            state_ = to ;
-    }
-
-private:
-
-    // --------------- parameters --------------------------
-    bool least_squares_ ;
-
-    // --------------- user representation --------------
-    unsigned int nb_variables_ ;
-    Variable* variable_ ;
-
-    // --------------- construction -----------------------
-    State state_ ;
-    unsigned int current_row_ ;
-    std::vector<CoeffType> af_ ;
-    std::vector<unsigned int> if_ ;
-    std::vector<CoeffType> al_ ;
-    std::vector<CoeffType> xl_ ;
-    double bk_ ;
-
-    // --------------- internal representation ---------
-    Matrix* A_ ;
-    Vector* x_ ;
-    Vector* b_ ;
-
-} ;
-
-
-} // namespace OpenNL
-
-#endif
diff --git a/OpenNL/package_info/OpenNL/dependencies b/OpenNL/package_info/OpenNL/dependencies
deleted file mode 100644
index e69de29bb2d1..000000000000
diff --git a/OpenNL/package_info/OpenNL/description.txt b/OpenNL/package_info/OpenNL/description.txt
deleted file mode 100644
index a04c250612ca..000000000000
--- a/OpenNL/package_info/OpenNL/description.txt
+++ /dev/null
@@ -1 +0,0 @@
-OpenNL (Open Numerical Library) is a library to easily construct and solve sparse linear systems.
diff --git a/OpenNL/package_info/OpenNL/license.txt b/OpenNL/package_info/OpenNL/license.txt
deleted file mode 100644
index 5c1c5d8436f8..000000000000
--- a/OpenNL/package_info/OpenNL/license.txt
+++ /dev/null
@@ -1 +0,0 @@
-LGPL (v3 or later)
diff --git a/OpenNL/package_info/OpenNL/long_description.txt b/OpenNL/package_info/OpenNL/long_description.txt
deleted file mode 100644
index 645de7254ee2..000000000000
--- a/OpenNL/package_info/OpenNL/long_description.txt
+++ /dev/null
@@ -1,23 +0,0 @@
-
-   --------------------- Open Numerical Library <T> -------------------------
-
-General information
-===================
-
-This is OpenNL<T>, a library to easily construct and solve sparse linear systems.
-
-* OpenNL<T> is supplied with a set of built-in iterative solvers
-   (Conjugate gradient and BICGSTAB)
-
-* OpenNL can also use other solvers (by writing a SolverTraits class)
-
-Contact
-=======
-
-The author is Bruno Levy <bruno.levy@loria.fr>.
-OpenNL main page is https://www.loria.fr/~levy/software/.
-
-Caution
-=======
-
-CGAL includes a version of OpenNL in C++, made especially for CGAL by Bruno Levy.
diff --git a/OpenNL/package_info/OpenNL/maintainer b/OpenNL/package_info/OpenNL/maintainer
deleted file mode 100644
index b4c1056278b5..000000000000
--- a/OpenNL/package_info/OpenNL/maintainer
+++ /dev/null
@@ -1 +0,0 @@
-Bruno Levy <Bruno.Levy@loria.fr>
diff --git a/Surface_mesh_parameterization/package_info/Surface_mesh_parameterization/dependencies b/Surface_mesh_parameterization/package_info/Surface_mesh_parameterization/dependencies
index e21fc4d23192..19c7b2f79832 100644
--- a/Surface_mesh_parameterization/package_info/Surface_mesh_parameterization/dependencies
+++ b/Surface_mesh_parameterization/package_info/Surface_mesh_parameterization/dependencies
@@ -15,7 +15,6 @@ Interval_support
 Kernel_23
 Modular_arithmetic
 Number_types
-OpenNL
 Polygon_mesh_processing
 Profiling_tools
 Property_map