Defence Secretary Ben Wallace has confirmed the UK will be the first country to donate long-range Storm Shadow missiles to Ukraine.
It comes after Ukraine's president, Volodymyr Zelensky visited the UK earlier this year and asked for fighter jets and long-range missiles to help his country defend itself against the Russian invasion.
The longer-range missiles will mean Ukrainian pilots can engage targets from a much greater range than previously.
Mr Wallace confirmed that he and Prime Minister Rishi Sunak had agreed to authorise the donation after continued Russian attacks on Ukraine.
He told the House of Commons: "Storm Shadow is a long-range, conventional-only, precision-strike capability. It complements the long-range systems already gifted, including Himars and Harpoon missiles, as well as Ukraine's own Neptune cruise missile."
He added: "The donation of these weapons systems gives Ukraine the best chance to defend themselves against Russia's continued brutality, especially the deliberate targeting of Ukrainian civilian infrastructure, which is against international law.
"Ukraine has a right to be able to defend itself against this."
Storm Shadow is the RAF's long-range cruise missile. It's a 'fire and forget' missile that is programmed before the mission and, with a maximum speed of 621mph, can hit targets 350 miles away.
According to defence analyst Dr James Bosbotinis, Storm Shadow will be "ideal" for targeting Russian facilities where fuel and munitions are stored before being sent to frontline units.
They would also be "ideal" for targeting Russian air and naval bases in Crimea, he added.