diff --git a/src/include/units/physical/si/mass.h b/src/include/units/physical/si/mass.h
index 7af3df31..4f8b6a56 100644
--- a/src/include/units/physical/si/mass.h
+++ b/src/include/units/physical/si/mass.h
@@ -30,6 +30,7 @@ namespace units::si {
 
 struct gram : named_unit<gram, "g", prefix> {};
 struct kilogram : prefixed_unit<kilogram, kilo, gram> {};
+struct tonne : named_scaled_unit<tonne, "t", prefix, ratio<1'0000>, kilogram> {};
 
 struct dim_mass : physical::dim_mass<kilogram> {};
 
@@ -46,6 +47,10 @@ constexpr auto operator""g(long double l) { return mass<gram, long double>(l); }
 constexpr auto operator""kg(unsigned long long l) { return mass<kilogram, std::int64_t>(l); }
 constexpr auto operator""kg(long double l) { return mass<kilogram, long double>(l); }
 
+// t
+constexpr auto operator""t(unsigned long long l) { return mass<tonne, std::int64_t>(l); }
+constexpr auto operator""t(long double l) { return mass<tonne, long double>(l); }
+
 }  // namespace literals
 
 }  // namespace units::si
diff --git a/test/unit_test/static/si_test.cpp b/test/unit_test/static/si_test.cpp
index 42ae4287..a6a54fc2 100644
--- a/test/unit_test/static/si_test.cpp
+++ b/test/unit_test/static/si_test.cpp
@@ -70,6 +70,7 @@ static_assert(kilometre::symbol == "km");
 // mass
 
 static_assert(1kg == 1000g);
+static_assert(1t == 1000kg);
 
 static_assert(kilogram::symbol == "kg");