These two teams are squaring off in a bid to join Leicester City and Ipswich Town in earning promotion to the Premier League.
Unsurprisingly, Daniel Farke has opted to select the Leeds XI that thrashed Norwich City by a 4-0 scoreline in the second leg of their semi-final.
That means that Archie Gray starts at right-back - rather than in central midfield - and Wilfried Gnonto features ahead of Daniel James on the flank.
There had been more doubt about the Southampton starting lineup with Che Adams in contention to return to the squad after injury.
Adams, who is expected to leave on a free transfer after this contest, is preferred to Sekou Mara on the substitutes' bench.
Russell Martin has decided to keep with the same team that posted a 3-1 win over West Bromwich Albion at St Mary's just over a week ago.
Leeds United: Meslier; Gray, Rodon, Ampadu, Firpo; Gruev, Kamara; Gnonto, Rutter, Summerville; Piroe
Subs: Darlow, Byram, Roberts, Cooper, Shackleton, Anthony, James, Gelhardt, Joseph
Southampton: McCarthy; Walker-Peters, Harwood-Bellis, Bednarek, Stephens; Aribo, Downes, Smallbone; Brooks, Armstrong, Fraser
Subs: Lumley, Bree, Manning, Charles, Rothwell, Edozie, Kamaldeen, Adams, Stewart