diff --git a/src/include/units/physical/natural/constants.h b/src/include/units/physical/natural/constants.h
new file mode 100644
index 00000000..4de79f28
--- /dev/null
+++ b/src/include/units/physical/natural/constants.h
@@ -0,0 +1,31 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/physical/natural/dimensions.h>
+
+namespace units::natural {
+
+inline constexpr auto speed_of_light = velocity<unitless>(1);
+
+}  // namespace units::natural
diff --git a/src/include/units/physical/natural/dimensions.h b/src/include/units/physical/natural/dimensions.h
new file mode 100644
index 00000000..bd570a61
--- /dev/null
+++ b/src/include/units/physical/natural/dimensions.h
@@ -0,0 +1,66 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/physical/dimensions.h>
+#include <units/physical/natural/units.h>
+#include <units/quantity.h>
+
+namespace units::natural {
+
+struct dim_length : physical::dim_length<inverted_gigaelectronvolt> {};
+template<Unit U, Scalar Rep = double>
+using length = quantity<dim_length, U, Rep>;
+
+struct dim_time : physical::dim_time<inverted_gigaelectronvolt> {};
+template<Unit U, Scalar Rep = double>
+using time = quantity<dim_time, U, Rep>;
+
+struct dim_mass : physical::dim_mass<gigaelectronvolt> {};
+template<Unit U, Scalar Rep = double>
+using mass = quantity<dim_mass, U, Rep>;
+
+struct dim_velocity : physical::dim_velocity<dim_velocity, unitless, dim_length, dim_time> {};
+template<Unit U, Scalar Rep = double>
+using velocity = quantity<dim_velocity, U, Rep>;
+
+struct dim_acceleration : physical::dim_acceleration<dim_acceleration, gigaelectronvolt, dim_length, dim_time> {};
+template<Unit U, Scalar Rep = double>
+using acceleration = quantity<dim_acceleration, U, Rep>;
+
+struct dim_force : physical::dim_force<dim_force, square_gigaelectronvolt, dim_mass, dim_acceleration> {};
+template<Unit U, Scalar Rep = double>
+using force = quantity<dim_force, U, Rep>;
+
+struct dim_momentum : physical::dim_momentum<dim_momentum, gigaelectronvolt, dim_mass, dim_velocity> {};
+template<Unit U, Scalar Rep = double>
+using momentum = quantity<dim_momentum, U, Rep>;
+
+struct dim_energy : physical::dim_energy<dim_energy, gigaelectronvolt, dim_force, dim_length> {};
+template<Unit U, Scalar Rep = double>
+using energy = quantity<dim_force, U, Rep>;
+
+// Typical UDLs will not work here as the same units are reused by many quantities.
+// Should we define some strange ones (i.e. q_mass_GeV)?
+
+}  // namespace units::natural
diff --git a/src/include/units/physical/natural/units.h b/src/include/units/physical/natural/units.h
new file mode 100644
index 00000000..b1454756
--- /dev/null
+++ b/src/include/units/physical/natural/units.h
@@ -0,0 +1,41 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/unit.h>
+#include <units/physical/si/prefixes.h>
+
+namespace units::natural {
+
+struct unitless : named_unit<unitless, "", no_prefix> {};
+struct electronvolt : named_unit<electronvolt, "eV", si::prefix> {};
+struct gigaelectronvolt : prefixed_unit<gigaelectronvolt, si::giga, electronvolt> {};
+struct inverted_gigaelectronvolt : named_unit<inverted_gigaelectronvolt, "GeV⁻¹", no_prefix> {};
+struct square_gigaelectronvolt : named_unit<square_gigaelectronvolt, "GeV²", no_prefix> {};
+
+// NOTE: eV as a base unit with no relation to joule prevents us from going back
+// from natural units to SI. Do we need such a support or should we treat
+// natural units as an isolated island with ev = 1 which simplifies all
+// the maths a lot?
+
+}  // namespace units::natural