Taylor Wimpey south divisional chairman Peter Truscott will take over the reins from October 1.
Truscott is an experienced house builder having worked at Wimpey and Cala Homes for more than 30 years.
Fitzgerald will become non-executive chairman of Galliford Try from next year.
Construction division chief executive Ken Gillespie has also been given a wider role and will become Chief Operating Officer while continuing to lead construction.
Fitzgerald said: “The Group has moved quickly to secure Peter Truscott as the new Chief Executive whilst further strengthening the Board.
“We have an excellent executive team, and a strong Board with a broad range of experience and skills. I am confident that the Group will move forward to build on our achievements to date and deliver our strategy of disciplined growth.”