The Taleban figure was Mullah Manan, who UK forces said was in the top tier of leadership and had been behind a large number of attacks.
Ten to 15 other Taleban were killed in what the UK forces called a "precision strike" in southern Helmand province.
Locals said about seven civilians died but this could not be confirmed.
The attack happened at about 0330 local time in a village called Lower Jal-jay, between two towns where British forces in Helmand have been fighting the Taleban.
Lt Col Rory Bruce, spokesman for the UK Task Force in the province, said Mullah Manan was a "Tier One" figure - an ideological fighter with links to the main Taleban leadership.
Col Bruce said troops had been tracking him for a number of weeks.
Mullah Manan was thought to be involved in the uprising in Musa Qala, a town nearby which British troops held, but is now controlled by the Taleban after a peace deal with elders broke down.
There has been heavy fighting in the Kajaki area of Helmand, where British forces are protecting a major dam reconstruction project.
Helmand has seen the most intense fighting between Nato forces and the Taleban this year, with many of its districts out of government control.
The BBC's Alastair Leithead in Kabul says Mullah Manan's death will be a step forward for Nato forces in Helmand, where Taleban reinforcements are thought to be gathering.
Earlier this week, the governor of the province said up to 700 insurgents had crossed over from Pakistan and were preparing to fight British forces.