Rickie Lambert's 18th goal of the season helped send Southampton to a first Wembley final since 1992 after a 4-1 aggregate win over MK Dons.
Saints won 3-1 on the night thanks to strikes from Lambert, Adam Lallana and a Danny Woodards own goal with Mark Randall responding for the Dons.
They will face Carlisle in the Wembley showpiece.
Lambert opened the scoring in the 15th minute after strike-partner Papa Waigo wriggled clear of his marker before feeding a pinpoint pass to Lambert to slot home from close range.
Saints` lead was doubled on the half hour after a comical own goal Woodards - an attempted clearance hitting him in the chest and dribbling past goalkeeper Willy Gueret.
Paul Ince's side pulled one back on the stroke of half-time through Randall`s neat 12-yard finish, but the home side remained on top.
The second half became a scrappy affair as the away side desperately tried to get back into the tie, but clear-cut chances remained at a premium even as Saints` defending became more nervous.
The impressive Lallana eventually made the game secure and confirmed Southampton's return to Wembley with a powerful finish in the 87th minute.
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