The 57-year-old had been in post since January 2019 and kept Accies in the top flight for two years before the club was relegated to the second tier at the end of the 2020/21 campaign. The South Lanarkshire side won 27 of his 101 games in charge, with Rice’s final involvement a 1-0 defeat by Morton.
Accies chairman Allan Maitland said: “Without any previous indications, we received a letter of resignation from Brian Rice. Whilst it has come as a surprise, we now fully understand his reasoning for leaving at this time and have, with regret, accepted his resignation.
“It has been an extremely difficult 18 months dealing with all the issues surrounding the pandemic, including the recent relegation from the Premiership, and there’s no doubt that it has taken its toll on Brian, his staff and everyone connected to the club.”
Accies currently lie fifth in the Championship with one point from their opening two matches.
A statement from the club read: “We would like to take this opportunity to thank Brian for his efforts and wish him every success in the future.”
Hamilton are next in action on Saturday, August 21 when they host Kilmarnock, having failed to progress from the Premier Sports Cup group stages despite winning two of their four matches.
C oaches Guillaume Beuzelin and Brian Potter are expected to take interim charge.