HMS Active was a Type 21-class frigate of the Royal Navy. Built by Vosper Thornycroft, Southampton, England, she was completed with Exocet launchers in 'B' position, the first of the class to be so fitted.
Active participated in the Falklands War, including firing on Argentine positions during the Battle of Mount Tumbledown. By the mid-1980s, in common with the other surviving Type 21s, Active suffered from hull cracking. When the ship was next refitted steel plating was welded along each side of the ship to repair and reinforce the weak points. At the same time modifications were made to reduce hull noise.
Active decommissioned and was sold to Pakistan on 23 September 1994, being renamed Shah Jahan. Exocet was not transferred to Pakistan and Shah Jahan had her obsolete Sea Cat launcher removed. A Chinese LY 60N missile launcher was fitted in place of the Exocet launchers. Signaal DA08 air search radar replaced the Type 992 and SRBOC chaff launchers and 20 mm and 30 mm guns were fitted.
Its flag was recently sold on the BBC programme Bargain Hunt. Shah Jahan remains in service with the Pakistan Navy. Between 11–21 May 2008, Shah Jahan participated in Exercise Inspired Union, an multi-national exercises in the North Arabian Sea. Other Pakistani warships included the frigate Badr and the replenishment tanker Nasr, as well as the Pakistan Air Force explosive ordnance disposal team, and the American destroyers Curts and Ross.