The former Livingston, Bradford City and Morton boss has agreed a two-year deal at Somerset Park ahead of Saturday's trip to play Hearts at Tynecastle.
Ayr chairman David Smith told the club website: "We are delighted to get our man! The number and quality of applications were excellent and we thank everyone who showed interest in becoming the manager of Ayr United.
"When we spoke to David, it became obvious that there is a synergy between what we as a club want to achieve and the aspirations and ambitions he has for Ayr United."
