The loss of Steve Wright will come as a shock to Radio1, which was showing the first signs of stemming the meltdown in its audience figures.
Mr Wright is leaving to pursue his career in television and to concentrate on his Home Truths programme on BBC1. He took over the Radio1 breakfast show in autumn 1993 to help revive flagging ratings at the same time as the removal of the stations' ageingDJs, such as Dave Lee Travis and Simon Bates.
Although his resignation was announced last night, Mr Wright is expected to continue presenting the Breakfast Show "for the foreseeable future," a spokesman for the BBC said.
The spokesman said no decision had been taken on who will take over as presenter of the popular early morning slot.
In his letter of resignation to the Radio1 controller Matthew Bannister, Mr Wright said: "I have enjoyed my 14 years with Radio1, none more so than the challenge of the Breakfast Show."
Mr Bannister confirmed that Mr Wright - recently voted the nation's most popular DJ by readers of Smash Hits magazine - was leaving to pursue his "burgeoning television career". "Steve has made a great contribution to Radio1 and we wish him great successin his television career," said Mr Bannister.
Mr Wright was recognised both inside and outside the BBC as one of its most innovative performers.
Although he did not create the zoo format - where many performers chatter together on the air - he certainly established the genre of broadcasting.
Together with his posse, Wright entertained listeners with his offbeat humour, spoof characters such as Mr Angry, The Newsagent and Voice Over Man, and his wacky True Stories snippets.
Despite the brave face Mr Bannister was putting on the resignation, the loss of Mr Wright will come as another blow to the station which has seen ratings slump in the wake of increased competition from commercial radio.Reuse content