diff --git a/tools/workspace/default.bzl b/tools/workspace/default.bzl
index 6b62b162cdd2..06e245e63dad 100644
--- a/tools/workspace/default.bzl
+++ b/tools/workspace/default.bzl
@@ -41,7 +41,6 @@ load("@drake//tools/workspace/gz_utils_internal:repository.bzl", "gz_utils_inter
 load("@drake//tools/workspace/ibex:repository.bzl", "ibex_repository")
 load("@drake//tools/workspace/intel_realsense_ros_internal:repository.bzl", "intel_realsense_ros_internal_repository")  # noqa
 load("@drake//tools/workspace/ipopt:repository.bzl", "ipopt_repository")
-load("@drake//tools/workspace/json:repository.bzl", "json_repository")
 load("@drake//tools/workspace/lapack:repository.bzl", "lapack_repository")
 load("@drake//tools/workspace/lcm:repository.bzl", "lcm_repository")
 load("@drake//tools/workspace/libblas:repository.bzl", "libblas_repository")
@@ -60,7 +59,6 @@ load("@drake//tools/workspace/mypy_extensions_internal:repository.bzl", "mypy_ex
 load("@drake//tools/workspace/mypy_internal:repository.bzl", "mypy_internal_repository")  # noqa
 load("@drake//tools/workspace/nanoflann_internal:repository.bzl", "nanoflann_internal_repository")  # noqa
 load("@drake//tools/workspace/net_sf_jchart2d:repository.bzl", "net_sf_jchart2d_repository")  # noqa
-load("@drake//tools/workspace/nlopt:repository.bzl", "nlopt_repository")
 load("@drake//tools/workspace/nlopt_internal:repository.bzl", "nlopt_internal_repository")  # noqa
 load("@drake//tools/workspace/openblas:repository.bzl", "openblas_repository")
 load("@drake//tools/workspace/opencl:repository.bzl", "opencl_repository")
@@ -200,8 +198,6 @@ def add_default_repositories(excludes = [], mirrors = DEFAULT_MIRRORS):
         intel_realsense_ros_internal_repository(name = "intel_realsense_ros_internal", mirrors = mirrors)  # noqa
     if "ipopt" not in excludes:
         ipopt_repository(name = "ipopt")
-    if "json" not in excludes:
-        json_repository(name = "json", mirrors = mirrors)
     if "lapack" not in excludes:
         lapack_repository(name = "lapack")
     if "lcm" not in excludes:
@@ -238,10 +234,6 @@ def add_default_repositories(excludes = [], mirrors = DEFAULT_MIRRORS):
         nanoflann_internal_repository(name = "nanoflann_internal", mirrors = mirrors)  # noqa
     if "net_sf_jchart2d" not in excludes:
         net_sf_jchart2d_repository(name = "net_sf_jchart2d", mirrors = mirrors)
-    if "nlopt" not in excludes:
-        # The @nlopt external is being removed from Drake on 2020-09-01.
-        # TODO(jwnimmer-tri) When removing @nlopt, also update install_prereqs.
-        nlopt_repository(name = "nlopt")
     if "nlopt_internal" not in excludes:
         nlopt_internal_repository(name = "nlopt_internal", mirrors = mirrors)
     if "openblas" not in excludes:
diff --git a/tools/workspace/json/BUILD.bazel b/tools/workspace/json/BUILD.bazel
deleted file mode 100644
index 7198e3bb9b53..000000000000
--- a/tools/workspace/json/BUILD.bazel
+++ /dev/null
@@ -1,5 +0,0 @@
-# -*- python -*-
-
-load("//tools/lint:lint.bzl", "add_lint_tests")
-
-add_lint_tests()
diff --git a/tools/workspace/json/package.BUILD.bazel b/tools/workspace/json/package.BUILD.bazel
deleted file mode 100644
index dd7c1bfdaf17..000000000000
--- a/tools/workspace/json/package.BUILD.bazel
+++ /dev/null
@@ -1,20 +0,0 @@
-# -*- python -*-
-
-load(
-    "@drake//tools/install:install.bzl",
-    "install",
-)
-
-licenses(["notice"])  # MIT
-
-package(
-    default_visibility = ["//visibility:public"],
-)
-
-cc_library(
-    name = "json",
-    hdrs = ["single_include/nlohmann/json.hpp"],
-    includes = ["single_include"],
-    defines = ["JSON_HAS_CPP_14"],  # Avoid <filesystem>.
-    deprecation = "DRAKE DEPRECATED: The @json external is being removed from Drake on or after 2020-09-01.  Downstream projects should add it to their own WORKSPACE if needed.",  # noqa
-)
diff --git a/tools/workspace/json/repository.bzl b/tools/workspace/json/repository.bzl
deleted file mode 100644
index f274be4fd35f..000000000000
--- a/tools/workspace/json/repository.bzl
+++ /dev/null
@@ -1,15 +0,0 @@
-# -*- python -*-
-
-load("@drake//tools/workspace:github.bzl", "github_archive")
-
-def json_repository(
-        name,
-        mirrors = None):
-    github_archive(
-        name = name,
-        repository = "nlohmann/json",
-        commit = "v3.10.5",
-        sha256 = "5daca6ca216495edf89d167f808d1d03c4a4d929cef7da5e10f135ae1540c7e4",  # noqa
-        build_file = ":package.BUILD.bazel",
-        mirrors = mirrors,
-    )
diff --git a/tools/workspace/nlopt/BUILD.bazel b/tools/workspace/nlopt/BUILD.bazel
deleted file mode 100644
index 2e5301dc6578..000000000000
--- a/tools/workspace/nlopt/BUILD.bazel
+++ /dev/null
@@ -1,8 +0,0 @@
-# -*- python -*-
-
-# This file exists to make our directory into a Bazel package, so that our
-# neighboring *.bzl file can be loaded elsewhere.
-
-load("//tools/lint:lint.bzl", "add_lint_tests")
-
-add_lint_tests()
diff --git a/tools/workspace/nlopt/package-macos.BUILD.bazel b/tools/workspace/nlopt/package-macos.BUILD.bazel
deleted file mode 100644
index f4106b631f09..000000000000
--- a/tools/workspace/nlopt/package-macos.BUILD.bazel
+++ /dev/null
@@ -1,25 +0,0 @@
-# -*- python -*-
-
-load(
-    "@drake_detected_os//:os.bzl",
-    "HOMEBREW_PREFIX",
-)
-
-licenses([
-    "notice",  # BSD-3-Clause AND MIT
-    "restricted",  # LGPL-2.1+
-])
-
-cc_library(
-    name = "nlopt",
-    srcs = ["include/nlopt.h"],
-    hdrs = ["include/nlopt.hpp"],
-    includes = ["include"],
-    linkopts = [
-        "-L{}/opt/nlopt/lib".format(HOMEBREW_PREFIX),
-        "-Wl,-rpath,{}/opt/nlopt/lib".format(HOMEBREW_PREFIX),
-        "-lnlopt",
-    ],
-    visibility = ["//visibility:public"],
-    deprecation = "DRAKE DEPRECATED: The @nlopt external is being removed from Drake on or after 2020-09-01.  Downstream projects should add it to their own WORKSPACE if needed.",  # noqa
-)
diff --git a/tools/workspace/nlopt/package-ubuntu-20.04.BUILD.bazel b/tools/workspace/nlopt/package-ubuntu-20.04.BUILD.bazel
deleted file mode 100644
index ef69027ee1a8..000000000000
--- a/tools/workspace/nlopt/package-ubuntu-20.04.BUILD.bazel
+++ /dev/null
@@ -1,19 +0,0 @@
-# -*- python -*-
-
-licenses([
-    "notice",  # BSD-3-Clause AND MIT
-    "restricted",  # LGPL-2.1+
-])
-
-cc_library(
-    name = "nlopt",
-    srcs = ["include/nlopt.h"],
-    hdrs = ["include/nlopt.hpp"],
-    includes = ["include"],
-    linkopts = [
-        "-L/usr/lib/x86_64-linux-gnu",
-        "-lnlopt_cxx",
-    ],
-    visibility = ["//visibility:public"],
-    deprecation = "DRAKE DEPRECATED: The @nlopt external is being removed from Drake on or after 2020-09-01.  Downstream projects should add it to their own WORKSPACE if needed.",  # noqa
-)
diff --git a/tools/workspace/nlopt/package-ubuntu-22.04.BUILD.bazel b/tools/workspace/nlopt/package-ubuntu-22.04.BUILD.bazel
deleted file mode 120000
index ef683c347a00..000000000000
--- a/tools/workspace/nlopt/package-ubuntu-22.04.BUILD.bazel
+++ /dev/null
@@ -1 +0,0 @@
-package-ubuntu-20.04.BUILD.bazel
\ No newline at end of file
diff --git a/tools/workspace/nlopt/repository.bzl b/tools/workspace/nlopt/repository.bzl
deleted file mode 100644
index dc8fccc2fa2f..000000000000
--- a/tools/workspace/nlopt/repository.bzl
+++ /dev/null
@@ -1,41 +0,0 @@
-# -*- mode: python -*-
-
-load("@drake//tools/workspace:os.bzl", "determine_os")
-
-def _impl(repository_ctx):
-    os_result = determine_os(repository_ctx)
-
-    if os_result.error != None:
-        fail(os_result.error)
-
-    if os_result.is_macos or os_result.is_macos_wheel:
-        build_flavor = "macos"
-        repository_ctx.symlink(
-            "{}/opt/nlopt/include/nlopt.h".format(os_result.homebrew_prefix),
-            "include/nlopt.h",
-        )
-        repository_ctx.symlink(
-            "{}/opt/nlopt/include/nlopt.hpp".format(os_result.homebrew_prefix),
-            "include/nlopt.hpp",
-        )
-    elif os_result.is_ubuntu or os_result.is_manylinux:
-        build_flavor = "ubuntu-{}".format(os_result.ubuntu_release)
-        repository_ctx.symlink("/usr/include/nlopt.h", "include/nlopt.h")
-        repository_ctx.symlink("/usr/include/nlopt.hpp", "include/nlopt.hpp")
-    else:
-        fail("Operating system is NOT supported {}".format(os_result))
-
-    repository_ctx.symlink(
-        Label(
-            "@drake//tools/workspace/nlopt:package-{}.BUILD.bazel".format(
-                build_flavor,
-            ),
-        ),
-        "BUILD.bazel",
-    )
-
-nlopt_repository = repository_rule(
-    local = True,
-    configure = True,
-    implementation = _impl,
-)