diff --git a/.editorconfig b/.editorconfig
index 0faa1c175..9633bf902 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -152,3 +152,7 @@ indent_size = 0
 trim_trailing_whitespace = false
 insert_final_newline = false
 end_of_line = lf
+
+[*.pro]
+indent_style = space
+indent_size = 0
diff --git a/book.json b/book.json
index 839600e50..f851e6744 100644
--- a/book.json
+++ b/book.json
@@ -185,6 +185,10 @@
           "lang": "lolcode",
           "name": "LOLCODE"
         },
+        {
+          "lang": "pro",
+          "name": "Prolog"
+        },
         {
           "lang": "piet",
           "name": "Piet"
diff --git a/contents/euclidean_algorithm/code/prolog/euclidean_algorithm.pro b/contents/euclidean_algorithm/code/prolog/euclidean_algorithm.pro
new file mode 100644
index 000000000..ea8a2e605
--- /dev/null
+++ b/contents/euclidean_algorithm/code/prolog/euclidean_algorithm.pro
@@ -0,0 +1,12 @@
+euclid_sub(A, A, A) :- !.
+euclid_sub(A, B, Result) :- A1 is abs(A), B1 is abs(B),
+                            A1 >  B1, !, T is A1 - B1, euclid_sub(T, B1, Result).
+euclid_sub(A, B, Result) :- A1 is abs(A), B1 is abs(B),
+                            A1 =< B1, !, T is B1 - A1, euclid_sub(A1, T, Result).
+
+euclid_mod(A, 0, A) :- !.
+euclid_mod(A, B, Result) :- A1 is abs(A), B1 is abs(B),
+                            M is mod(A1, B1), euclid_mod(B1, M, Result).
+
+test_euclid_sub(Result) :- euclid_sub(4288, 5184, Result). % Result: 64
+test_euclid_mod(Result) :- euclid_mod(1536, 9856, Result). % Result: 128 
diff --git a/contents/euclidean_algorithm/euclidean_algorithm.md b/contents/euclidean_algorithm/euclidean_algorithm.md
index 967e4b5f9..7d0cb007b 100644
--- a/contents/euclidean_algorithm/euclidean_algorithm.md
+++ b/contents/euclidean_algorithm/euclidean_algorithm.md
@@ -65,6 +65,8 @@ The algorithm is a simple way to find the *greatest common divisor* (GCD) of two
 [import:25-40, lang="LOLCODE"](code/lolcode/euclid.lol)
 {% sample lang="bash" %}
 [import:24-38, lang="bash"](code/bash/euclid.bash)
+{% sample lang="pro" %}
+[import:1-5, lang="Prolog"](code/prolog/euclidean_algorithm.pro)
 {% sample lang="piet" %}
 > ![](code/piet/subtract/euclidian_algorithm_subtract_large.png) ![](code/piet/subtract/euclidian_algorithm_subtract.png)
 {% sample lang="ss" %}
@@ -140,6 +142,8 @@ Modern implementations, though, often use the modulus operator (%) like so
 [import:9-23, lang="LOLCODE"](code/lolcode/euclid.lol)
 {% sample lang="bash" %}
 [import:10-22, lang="bash"](code/bash/euclid.bash)
+{% sample lang="pro" %}
+[import:7-10, lang="Prolog"](code/prolog/euclidean_algorithm.pro)
 {% sample lang="piet" %}
 > ![](code/piet/mod/euclidian_algorithm_mod_large.png) ![](code/piet/mod/euclidian_algorithm_mod.png)
 {% sample lang="ss" %}
@@ -229,6 +233,8 @@ and modulo method:
 [import, lang="LOLCODE"](code/lolcode/euclid.lol)
 {% sample lang="bash" %}
 [import, lang="bash"](code/bash/euclid.bash)
+{% sample lang="pro" %}
+[import, lang="Prolog"](code/prolog/euclidean_algorithm.pro)
 {% sample lang="piet" %}
 A text version of the program is provided for both versions.
 #### Subtraction