diff --git a/storm/Big.cpp b/storm/Big.cpp
index 291f6de..8723c94 100644
--- a/storm/Big.cpp
+++ b/storm/Big.cpp
@@ -107,6 +107,10 @@ void SBigNot(BigData* a, BigData* b) {
     Not(a->Primary(), b->Primary());
 }
 
+void SBigOr(BigData* a, BigData* b, BigData* c) {
+    Or(a->Primary(), b->Primary(), c->Primary());
+}
+
 void SBigPowMod(BigData* a, BigData* b, BigData* c, BigData* d) {
     PowMod(a->Primary(), b->Primary(), c->Primary(), d->Primary(), a->Stack());
 }
diff --git a/storm/Big.hpp b/storm/Big.hpp
index 595b872..4daeea3 100644
--- a/storm/Big.hpp
+++ b/storm/Big.hpp
@@ -44,6 +44,8 @@ void SBigNew(BigData** num);
 
 void SBigNot(BigData* a, BigData* b);
 
+void SBigOr(BigData* a, BigData* b, BigData* c);
+
 void SBigPowMod(BigData* a, BigData* b, BigData* c, BigData* d);
 
 void SBigShl(BigData* a, BigData* b, uint32_t shift);
diff --git a/storm/big/Ops.cpp b/storm/big/Ops.cpp
index 3f49e12..cc51358 100644
--- a/storm/big/Ops.cpp
+++ b/storm/big/Ops.cpp
@@ -286,6 +286,15 @@ void Not(BigBuffer& a, const BigBuffer& b) {
     a.SetCount(i);
 }
 
+void Or(BigBuffer& a, const BigBuffer& b, const BigBuffer& c) {
+    uint32_t i = 0;
+    for (; b.IsUsed(i) || c.IsUsed(i); i++) {
+        a[i] = c[i] | b[i];
+    }
+
+    a.SetCount(i);
+}
+
 void PowMod(BigBuffer& a, const BigBuffer& b, const BigBuffer& c, const BigBuffer& d, BigStack& stack) {
     c.Trim();
 
diff --git a/storm/big/Ops.hpp b/storm/big/Ops.hpp
index ce75b49..ef523db 100644
--- a/storm/big/Ops.hpp
+++ b/storm/big/Ops.hpp
@@ -51,6 +51,8 @@ void MulMod(BigBuffer& a, const BigBuffer& b, const BigBuffer& c, const BigBuffe
 
 void Not(BigBuffer& a, const BigBuffer& b);
 
+void Or(BigBuffer& a, const BigBuffer& b, const BigBuffer& c);
+
 void PowMod(BigBuffer& a, const BigBuffer& b, const BigBuffer& c, const BigBuffer& d, BigStack& stack);
 
 void SetOne(BigBuffer& buffer);
diff --git a/test/Big.cpp b/test/Big.cpp
index b7d1218..e3b95b6 100644
--- a/test/Big.cpp
+++ b/test/Big.cpp
@@ -769,6 +769,56 @@ TEST_CASE("SBigNot", "[big]") {
     }
 }
 
+TEST_CASE("SBigOr", "[big]") {
+    BigDataTest a, b, c;
+
+    SECTION("performs bitwise or on small numbers") {
+        auto v = GENERATE(
+            std::make_pair(0UL, 0UL),
+            std::make_pair(0UL, 123UL),
+            std::make_pair(41689UL, 786740UL)
+        );
+
+        SBigFromUnsigned(b, v.first);
+        SBigFromUnsigned(c, v.second);
+        SBigOr(a, b, c);
+
+        CHECK(a->Primary().Count() == 1);
+        CHECK(a->Primary()[0] == (v.first | v.second));
+    }
+
+    SECTION("performs bitwise or on large numbers") {
+        auto v = GENERATE(
+            std::make_pair(0xFF00FF00FF00FF00ULL, 0xFF00FF00FF00FFULL)
+        );
+
+        SBigFromStr(b, std::to_string(v.first).c_str());
+        SBigFromStr(c, std::to_string(v.second).c_str());
+        SBigOr(a, b, c);
+
+        CHECK(a->Primary().Count() == 2);
+        CHECK(a->Primary()[0] == uint32_t(v.first | v.second));
+        CHECK(a->Primary()[1] == uint32_t((v.first | v.second) >> 32));
+    }
+
+    SECTION("performs bitwise or on huge value") {
+        uint32_t data[] = { 0xF00DFEEDUL, 0xBA1DUL, 0xBEEBBEEBUL, 0x12345678UL, 0x9ABCDEFUL, 0xDEADCADUL, 0xD011AUL };
+
+        SBigFromBinary(b, data, sizeof(data));
+        SBigFromUnsigned(c, 0x11111111UL);
+        SBigOr(a, b, c);
+
+        CHECK(a->Primary().Count() == 7);
+        CHECK(a->Primary()[0] == 0xF11DFFFD);
+        CHECK(a->Primary()[1] == data[1]);
+        CHECK(a->Primary()[2] == data[2]);
+        CHECK(a->Primary()[3] == data[3]);
+        CHECK(a->Primary()[4] == data[4]);
+        CHECK(a->Primary()[5] == data[5]);
+        CHECK(a->Primary()[6] == data[6]);
+    }
+}
+
 TEST_CASE("SBigShl", "[big]") {
     SECTION("shifts 256 left 7 bits") {
         BigData* a;