The Brandywell will host the EA Sports Cup final for the second year running.
Last year's Cup winners Derry City will face Dundalk at the ground after the Candystripes won the home team draw earlier today.
The clubs will meet in a Premier Division clash at the same venue on Friday night.
The Cup final will kick-off at 8pm on Saturday, September 14 and it means that the SSE Airtricity League game between Dundalk and Shamrock Rovers, scheduled for Friday, 13 September, has been postponed.
Derry won the EA Sports Cup for a record 11th time by beating Cobh Ramblers in last year's final and reached this year's decider by beating Waterford after extra time in the semi-final.
Dundalk, meanwhile, hammered Bohemians 6-1 to make it to the final for the third time in the last six years. The Lilywhites won the competition in 2014 and '17.
The SSE Airtricity League Premier Division fixture between Sligo Rovers and Dundalk at the Showgrounds has been rescheduled for Monday, September 2nd at 7.45pm.
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