Nottingham Forest and Huddersfield Town are playing for promotion to the Premier League.
Nottingham beat Sheffield United 3-2 on penalties in the second leg of the semi-final on Tuesday night.
In regular time, Forest lost 1:2, so that the sum of both duels was 3:3 and the penalty shoot-out had to decide.
There, Forest goalkeeper Brice Samba became man of the evening with three saves.
Huddersfield had previously secured a place in the Championship play-off final against Luton Town on May 29 at London's Wembley Stadium.
"Assault"
After Nottingham reached the final, Sheffield captain Billy Sharp, who was not used and was standing on the sidelines, was allegedly attacked by a fan when thousands of Forest fans stormed the field.
Video footage shows the man running at Sharp, headbutting him and throwing him to the ground with full force.
Sheffield manager Paul Heckingbottom described the incident as an "assault" and promised the perpetrator "will be held accountable".
Nottingham Forest said they are working with the relevant authorities to locate the perpetrator, who is to be given a lifetime stadium ban.
Sharp had played for Nottingham Forest on loan in the 2012/2013 season.
Nottingham, who won the English Championship in 1978, the European Cup in 1979 and 1980 and the FA Cup twice, last played in the Premier League in 1999.
Huddersfield were promoted to the English top flight for the first time since the Premier League was launched in 1992 in 2017, before being relegated to the Championship in 2019.