Emma Raducanu was targeted by a man who "exhibited fixated behaviour" during her second-round loss to Karolina Muchova at the Dubai Tennis Championships, the WTA said.
An emotional Raducanu, 22, was seen hiding behind the umpire's chair two games into the defeat by Muchova.
"On Monday, February 17, Emma Raducanu was approached in a public area by a man who exhibited fixated behaviour," said the Women's Tennis Association.
"This same individual was identified in the first few rows during Emma's match on Tuesday and subsequently ejected."
The man has been banned from all WTA events, "pending a threat assessment".