Easy win
Martin turned the ball home from only yards out after latching onto a headed flick from Frazier Campbell.
Carlos Tevez and Michael Carrick had early chances before the deadlock was broken with on-form Pirates 'keeper Senzo Meyiwa kept busy throughout.
United were a lot quieter after the interval with Sir Alex Ferguson making five second-half changes.
However, the Pirates frontline failed to cause the tourists any genuine problems and United will be pleased with a comfortable result.
A mention has to go the Orlando supporters who were fantastic throughout. They made a supern amount of noise - but their players couldn't quite find the performance to match.
The Pirates now face arch-rivals the Kaizer Chiefs to determine who will play United for a second time with the Vodacom Challenge Cup trophy on the line.
Full Time - Orlando Pirates 0-1 Manchester United
Attendance - 50,000
Manchester United: Foster, Brown, Ferdinand, Evans (Simpson 88), Silvestre (O'Shea 62), Eagles, Carrick (Scholes 69), Gibson (Fletcher 82), Martin, Tevez (Rooney 69), Campbell.
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