Wasps director of rugby Dai Young is to 'step back' from first-team duties with the Coventry-based Premiership club for an unspecified period.
Former dual code Wales international Young, 52, has been Wasps boss since their High Wycombe days, having been appointed in 2011.
Lee Blackett, 37, who is part of Young's backroom team, will step up to become interim head coach.
Wasps are currently ninth in the Premiership table after nine games.
They have only won 13 of their last 46 matches in all competitions and have been knocked out of Europe early in the last two seasons.
They have also lost a lot of their big names in that period, most notably England's Elliot Daly to Saracens last summer, as well as World Cup winner Willie Le Roux, Kurtley Beale, Danny Cipriani, James Haskell, Guy Thompson and also Christian Wade to American football.
Attack and backs coach Blackett has been with Wasps since arriving from Rotherham Titans in 2015.
Wasps' club statement said: "Director of Rugby Dai Young will be stepping back from first-team duties for an interim period.
"Lee Blackett will step up to interim head coach. Further announcements will be made in due course."
Blackett's first game in charge will be Wasps' return to action after a three-week break at Leicester on Saturday.
They went into the enforced break after a thrilling 30-26 comeback win at Worcester, which included two stunning tries by wing Zach Kibirige and twice-capped England scrum-half Dan Robson.
Analysis
BBC Coventry & Warwickshire's Alec Blackman
"It's a move that's taken some fans by surprise, but Wasps have struggled in the last two seasons, since losing the Premiership final to Exeter in 2017.
"The team that Dai Young took to the final has been broken up, with Danny Cipriani moving to Gloucester, James Haskell going to Northampton before retiring, Guy Thompson choosing to play for Leicester and Elliot Daly going to Saracens.
"Losing prolific try-scorer Christian Wade to a potential career in the NFL at the start of the 2018-19 season was also a blow.
"But results show that, of their last 46 games in all competitions, Wasps have won just 13 under Young's stewardship."