Off-court coaching will be allowed in tennis from January 2025, the International Tennis Federation (ITF) has announced.
The decision was made at the governing body's annual general meeting and follows recent trials on the men's ATP and women's WTA tours.
The ITF says the move will make tennis "fairer and, potentially, more entertaining".
The new changes mean:
Coaches can issue advice either verbally or via hand signals at any time except during the playing of a point.
Coaching must be "brief and discreet", except during breaks in play.
In team events only, where a team captain sits on court, the team captain may also give coaching advice.
Players can access approved "player analysis technology" at times when coaching is permitted.
The decision whether to implement the rule changes will be at the jurisdiction of the sanctioning body of each individual tournament or event.
Coaching during matches has been controversial in the past, with some players accused of illegally receiving advice - including an outburst from Daniil Medvedev in his match against Stefanos Tsitsipas at the 2022 Australian Open.
Former world number 10 Denis Shapovalov has criticised the change, writing on X:, external "Not just as a tennis player but as a fan of this sport it's sad to see this new off-court coaching rule.
"Tennis is special because you are out there alone. Why are you trying to change the beauty of this game?"
Stuart Miller, ITF senior executive director for integrity and legal, said: "We’ve gathered feedback from all key stakeholders including players, coaches and chair umpires.
"Players felt it was a positive development and makes tournaments more interesting for them."