diff --git a/contrib/atf/atf-c++/check.hpp b/contrib/atf/atf-c++/check.hpp
--- a/contrib/atf/atf-c++/check.hpp
+++ b/contrib/atf/atf-c++/check.hpp
@@ -71,7 +71,7 @@
     check_result(const atf_check_result_t* result);
 
     friend check_result test_constructor(const char* const*);
-    friend std::auto_ptr< check_result > exec(const atf::process::argv_array&);
+    friend std::unique_ptr< check_result > exec(const atf::process::argv_array&);
 
 public:
     //!
@@ -120,7 +120,7 @@
                const atf::process::argv_array&);
 bool build_cxx_o(const std::string&, const std::string&,
                  const atf::process::argv_array&);
-std::auto_ptr< check_result > exec(const atf::process::argv_array&);
+std::unique_ptr< check_result > exec(const atf::process::argv_array&);
 
 // Useful for testing only.
 check_result test_constructor(void);
diff --git a/contrib/atf/atf-c++/check.cpp b/contrib/atf/atf-c++/check.cpp
--- a/contrib/atf/atf-c++/check.cpp
+++ b/contrib/atf/atf-c++/check.cpp
@@ -141,7 +141,7 @@
     return success;
 }
 
-std::auto_ptr< impl::check_result >
+std::unique_ptr< impl::check_result >
 impl::exec(const atf::process::argv_array& argva)
 {
     atf_check_result_t result;
@@ -150,5 +150,5 @@
     if (atf_is_error(err))
         throw_atf_error(err);
 
-    return std::auto_ptr< impl::check_result >(new impl::check_result(&result));
+    return std::unique_ptr< impl::check_result >(new impl::check_result(&result));
 }
diff --git a/contrib/atf/atf-c++/check_test.cpp b/contrib/atf/atf-c++/check_test.cpp
--- a/contrib/atf/atf-c++/check_test.cpp
+++ b/contrib/atf/atf-c++/check_test.cpp
@@ -52,7 +52,7 @@
 // ------------------------------------------------------------------------
 
 static
-std::auto_ptr< atf::check::check_result >
+std::unique_ptr< atf::check::check_result >
 do_exec(const atf::tests::tc* tc, const char* helper_name)
 {
     std::vector< std::string > argv;
@@ -65,7 +65,7 @@
 }
 
 static
-std::auto_ptr< atf::check::check_result >
+std::unique_ptr< atf::check::check_result >
 do_exec(const atf::tests::tc* tc, const char* helper_name, const char *carg2)
 {
     std::vector< std::string > argv;
@@ -248,11 +248,11 @@
 }
 ATF_TEST_CASE_BODY(exec_cleanup)
 {
-    std::auto_ptr< atf::fs::path > out;
-    std::auto_ptr< atf::fs::path > err;
+    std::unique_ptr< atf::fs::path > out;
+    std::unique_ptr< atf::fs::path > err;
 
     {
-        std::auto_ptr< atf::check::check_result > r =
+        std::unique_ptr< atf::check::check_result > r =
             do_exec(this, "exit-success");
         out.reset(new atf::fs::path(r->stdout_path()));
         err.reset(new atf::fs::path(r->stderr_path()));
@@ -272,7 +272,7 @@
 ATF_TEST_CASE_BODY(exec_exitstatus)
 {
     {
-        std::auto_ptr< atf::check::check_result > r =
+        std::unique_ptr< atf::check::check_result > r =
             do_exec(this, "exit-success");
         ATF_REQUIRE(r->exited());
         ATF_REQUIRE(!r->signaled());
@@ -280,7 +280,7 @@
     }
 
     {
-        std::auto_ptr< atf::check::check_result > r =
+        std::unique_ptr< atf::check::check_result > r =
             do_exec(this, "exit-failure");
         ATF_REQUIRE(r->exited());
         ATF_REQUIRE(!r->signaled());
@@ -288,7 +288,7 @@
     }
 
     {
-        std::auto_ptr< atf::check::check_result > r =
+        std::unique_ptr< atf::check::check_result > r =
             do_exec(this, "exit-signal");
         ATF_REQUIRE(!r->exited());
         ATF_REQUIRE(r->signaled());
@@ -321,12 +321,12 @@
 }
 ATF_TEST_CASE_BODY(exec_stdout_stderr)
 {
-    std::auto_ptr< atf::check::check_result > r1 =
+    std::unique_ptr< atf::check::check_result > r1 =
         do_exec(this, "stdout-stderr", "result1");
     ATF_REQUIRE(r1->exited());
     ATF_REQUIRE_EQ(r1->exitcode(), EXIT_SUCCESS);
 
-    std::auto_ptr< atf::check::check_result > r2 =
+    std::unique_ptr< atf::check::check_result > r2 =
         do_exec(this, "stdout-stderr", "result2");
     ATF_REQUIRE(r2->exited());
     ATF_REQUIRE_EQ(r2->exitcode(), EXIT_SUCCESS);
@@ -372,7 +372,7 @@
     argv.push_back("/foo/bar/non-existent");
 
     atf::process::argv_array argva(argv);
-    std::auto_ptr< atf::check::check_result > r = atf::check::exec(argva);
+    std::unique_ptr< atf::check::check_result > r = atf::check::exec(argva);
     ATF_REQUIRE(r->exited());
     ATF_REQUIRE_EQ(r->exitcode(), 127);
 }
diff --git a/contrib/atf/atf-c++/detail/process_test.cpp b/contrib/atf/atf-c++/detail/process_test.cpp
--- a/contrib/atf/atf-c++/detail/process_test.cpp
+++ b/contrib/atf/atf-c++/detail/process_test.cpp
@@ -196,8 +196,8 @@
     const char* const carray1[] = { "arg1", NULL };
     const char* const carray2[] = { "arg1", "arg2", NULL };
 
-    std::auto_ptr< argv_array > argv1(new argv_array(carray1));
-    std::auto_ptr< argv_array > argv2(new argv_array(carray2));
+    std::unique_ptr< argv_array > argv1(new argv_array(carray1));
+    std::unique_ptr< argv_array > argv2(new argv_array(carray2));
 
     *argv2 = *argv1;
     ATF_REQUIRE_EQ(argv2->size(), argv1->size());
@@ -226,8 +226,8 @@
 
     const char* const carray[] = { "arg0", NULL };
 
-    std::auto_ptr< argv_array > argv1(new argv_array(carray));
-    std::auto_ptr< argv_array > argv2(new argv_array(*argv1));
+    std::unique_ptr< argv_array > argv1(new argv_array(carray));
+    std::unique_ptr< argv_array > argv2(new argv_array(*argv1));
 
     ATF_REQUIRE_EQ(argv2->size(), argv1->size());
     ATF_REQUIRE(std::strcmp((*argv2)[0], (*argv1)[0]) == 0);
diff --git a/contrib/atf/atf-sh/atf-check.cpp b/contrib/atf/atf-sh/atf-check.cpp
--- a/contrib/atf/atf-sh/atf-check.cpp
+++ b/contrib/atf/atf-sh/atf-check.cpp
@@ -108,7 +108,7 @@
 };
 
 class temp_file : public std::ostream {
-    std::auto_ptr< atf::fs::path > m_path;
+    std::unique_ptr< atf::fs::path > m_path;
     int m_fd;
 
 public:
@@ -414,7 +414,7 @@
 }
 
 static
-std::auto_ptr< atf::check::check_result >
+std::unique_ptr< atf::check::check_result >
 execute(const char* const* argv)
 {
     // TODO: This should go to stderr... but fixing it now may be hard as test
@@ -430,7 +430,7 @@
 }
 
 static
-std::auto_ptr< atf::check::check_result >
+std::unique_ptr< atf::check::check_result >
 execute_with_shell(char* const* argv)
 {
     const std::string cmd = flatten_argv(argv);
@@ -916,7 +916,7 @@
         m_stderr_checks.push_back(output_check(oc_empty, false, ""));
 
     do {
-        std::auto_ptr< atf::check::check_result > r =
+        std::unique_ptr< atf::check::check_result > r =
             m_xflag ? execute_with_shell(m_argv) : execute(m_argv);
 
         if ((run_status_checks(m_status_checks, *r) == false) ||
diff --git a/lib/atf/Makefile.inc b/lib/atf/Makefile.inc
--- a/lib/atf/Makefile.inc
+++ b/lib/atf/Makefile.inc
@@ -27,6 +27,3 @@
 CFLAGS+=	-DHAVE_CONFIG_H
 
 WARNS?=		3
-
-# Permit use of auto_ptr for compilers defaulting to C++17 or later
-CXXSTD=		c++11
diff --git a/lib/atf/libatf-c++/Makefile b/lib/atf/libatf-c++/Makefile
--- a/lib/atf/libatf-c++/Makefile
+++ b/lib/atf/libatf-c++/Makefile
@@ -48,9 +48,6 @@
 
 CFLAGS+=	-DHAVE_CONFIG_H
 
-# Silence warnings about usage of deprecated std::auto_ptr
-CXXWARNFLAGS+=	-Wno-deprecated-declarations
-
 SRCS=		application.cpp \
 		build.cpp \
 		check.cpp \
diff --git a/libexec/atf/atf-check/Makefile b/libexec/atf/atf-check/Makefile
--- a/libexec/atf/atf-check/Makefile
+++ b/libexec/atf/atf-check/Makefile
@@ -38,10 +38,6 @@
 CFLAGS+=	-I${ATF}
 CFLAGS+=	-DATF_SHELL='"/bin/sh"'
 
-# Silence warnings about usage of deprecated std::auto_ptr
-CXXWARNFLAGS+=	-Wno-deprecated-declarations
-CXXSTD=		c++11
-
 LIBADD=		atf_cxx
 
 HAS_TESTS=
diff --git a/libexec/atf/atf-sh/Makefile b/libexec/atf/atf-sh/Makefile
--- a/libexec/atf/atf-sh/Makefile
+++ b/libexec/atf/atf-sh/Makefile
@@ -65,9 +65,6 @@
 CFLAGS+=	-DATF_SHELL='"/bin/sh"'
 CFLAGS+=	-I${ATF}
 
-# Silence warnings about usage of deprecated std::auto_ptr
-CXXWARNFLAGS+=	-Wno-deprecated-declarations
-
 LIBADD=		atf_cxx
 
 FILESGROUPS=	SUBR
diff --git a/share/mk/atf.test.mk b/share/mk/atf.test.mk
--- a/share/mk/atf.test.mk
+++ b/share/mk/atf.test.mk
@@ -55,8 +55,6 @@
 .endif
 TEST_INTERFACE.${_T}= atf
 .endfor
-# Silence warnings about usage of deprecated std::auto_ptr
-CXXWARNFLAGS+=	-Wno-deprecated-declarations
 .endif
 
 .if !empty(ATF_TESTS_SH)