diff --git a/gnu/packages/cpp.scm b/gnu/packages/cpp.scm
index b5adcd8bcc..9a3eeee195 100644
--- a/gnu/packages/cpp.scm
+++ b/gnu/packages/cpp.scm
@@ -57,6 +57,7 @@
   #:use-module (guix build-system gnu)
   #:use-module (guix build-system meson)
   #:use-module (guix build-system python)
+  #:use-module (guix build-system scons)
   #:use-module (guix modules)
   #:use-module (guix gexp)
   #:use-module (gnu packages)
@@ -2036,3 +2037,67 @@ functions for the float and double types.")
 computing Fast Fourier transformations.  It supports multidimensional arrays,
 different floating point sizes and complex transformations.")
       (license license:bsd-3))))
+
+(define-public sajson
+  (let ((commit "ec644013e34f9984a3cc9ba568cab97a391db9cd")
+        (revision "0"))
+    (package
+      (name "sajson")
+      (version (git-version "1.0" revision commit))
+      (source (origin
+                (method git-fetch)
+                (uri (git-reference
+                      (url "https://github.com/chadaustin/sajson")
+                      (commit commit)))
+                (file-name (git-file-name name version))
+                (patches
+                 (search-patches "sajson-build-with-gcc10.patch"))
+                (sha256
+                 (base32
+                  "0fjag27w7gvkc5pdhq3ad7yc09rabpzahndw1sgsg04ipznidmmq"))
+                (modules '((guix build utils)))
+                (snippet '(delete-file-recursively "third-party"))))
+      (build-system scons-build-system)
+      (arguments
+       (list
+        #:phases
+        #~(modify-phases %standard-phases
+            (add-after 'unpack 'disable-other-builds
+              (lambda _
+                (substitute* "SConstruct"
+                  (("for name, tools in builds:")
+                   "for name, tools in [('opt', [gcc, opt])]:"))))
+            (add-after 'unpack 'use-external-unittest-cpp
+              (lambda _
+                (substitute* "SConscript"
+                  (("unittestpp_env\\.Library") "_dummy = ")
+                  (("test_env = env.Clone\\(tools=\\[unittestpp, sajson\\]\\)")
+                   (string-append
+                    "test_env = env.Clone(tools=[sajson])\n"
+                    "test_env.Append(CPPPATH='"
+                    (search-input-directory %build-inputs "/include/UnitTest++")
+                    "', LIBPATH='"
+                    (string-append #$(this-package-native-input "unittest-cpp")
+                                   "/lib")
+                    "', LIBS=['UnitTest++'])")))))
+            (replace 'build
+              (lambda* (#:key tests? #:allow-other-keys #:rest args)
+                (when tests?
+                  (apply (assoc-ref %standard-phases 'build)
+                         args))))
+            (replace 'check
+              (lambda* (#:key tests? #:allow-other-keys)
+                (when tests?
+                  (invoke "build/opt/test")
+                  (invoke "build/opt/test_unsorted"))))
+            (replace 'install
+              (lambda _
+                (let ((out (string-append #$output "/include")))
+                  (install-file "include/sajson.h" out)
+                  (install-file "include/sajson_ostream.h" out)))))))
+      (native-inputs (list unittest-cpp))
+      (home-page "https://github.com/chadaustin/sajson")
+      (synopsis "C++11 header-only, in-place JSON parser")
+      (description "@code{sajson} is an in-place JSON parser with support for
+parsing with only a single memory allocation.")
+      (license license:expat))))
diff --git a/gnu/packages/patches/sajson-build-with-gcc10.patch b/gnu/packages/patches/sajson-build-with-gcc10.patch
new file mode 100644
index 0000000000..878706dc79
--- /dev/null
+++ b/gnu/packages/patches/sajson-build-with-gcc10.patch
@@ -0,0 +1,45 @@
+This patch is from the upstream pull request
+https://github.com/chadaustin/sajson/pull/54.
+It fixes linking with GCC.
+
+diff --git a/include/sajson.h b/include/sajson.h
+index 8b4e05a..1bd045b 100644
+--- a/include/sajson.h
++++ b/include/sajson.h
+@@ -138,12 +138,17 @@ constexpr inline size_t make_element(tag t, size_t value) {
+ // header. This trick courtesy of Rich Geldreich's Purple JSON parser.
+ template <typename unused = void>
+ struct globals_struct {
++    static const unsigned char parse_flags[256];
++};
++typedef globals_struct<> globals;
++
+ // clang-format off
+ 
+     // bit 0 (1) - set if: plain ASCII string character
+     // bit 1 (2) - set if: whitespace
+     // bit 4 (0x10) - set if: 0-9 e E .
+-    constexpr static const uint8_t parse_flags[256] = {
++    template <typename unused>
++    const unsigned char globals_struct<unused>::parse_flags[256] = {
+      // 0    1    2    3    4    5    6    7      8    9    A    B    C    D    E    F
+         0,   0,   0,   0,   0,   0,   0,   0,     0,   2,   2,   0,   0,   2,   0,   0, // 0
+         0,   0,   0,   0,   0,   0,   0,   0,     0,   0,   0,   0,   0,   0,   0,   0, // 1
+@@ -162,15 +167,13 @@ struct globals_struct {
+     };
+ 
+ // clang-format on
+-};
+-typedef globals_struct<> globals;
+ 
+-constexpr inline bool is_plain_string_character(char c) {
++inline bool is_plain_string_character(char c) {
+     // return c >= 0x20 && c <= 0x7f && c != 0x22 && c != 0x5c;
+     return (globals::parse_flags[static_cast<unsigned char>(c)] & 1) != 0;
+ }
+ 
+-constexpr inline bool is_whitespace(char c) {
++inline bool is_whitespace(char c) {
+     // return c == '\r' || c == '\n' || c == '\t' || c == ' ';
+     return (globals::parse_flags[static_cast<unsigned char>(c)] & 2) != 0;
+ }