The 23-year-old forward spent just a single season with the Blues, making 47 appearances, scoring three goals and providing five assists in all competitions in an underwhelming season since joining from Ipswich Town.
Delap has opened up on his latest move after committing to a five-year contract with the City Ground based outfit.
"This is a massive club with a big history," said the Englishman.
"I spoke to the manager (Oliver Glasner) and I like his way, I think he can be the one to really help me develop and make that next step and hopefully I can bring goals here.
"As a team we can build something really strong and the main aim is to challenge and be a top club in the Premier League."
He joins attacking midfielder Gustavo Sa, central midfielder Xaver Schlager and centre-back Ousmane Diomane as the Tricky Trees latest recruits for the 2026/27 season following the departures of Elliot Anderson, Taiwo Awoniyi and others.