Former US Open champion Cilic, who beat Novak Djokovic for the title last year, will once again use the tournament to fine-tune his preparation for Wimbledon.

“Winning the (title) last year was one of the highlights of my career,” Cilic, who also triumphed in 2012, said in a statement.

“It was a close final and fightback against Novak and came after I was narrowly beaten by Feliciano Lopez in the final a year earlier.

“I have always loved playing at the Queen’s Club, and it will be a special feeling to try to defend my title in 2019.”

Tsitsipas, who stunned 20-times Grand Slam champion Roger Federer at last month’s Australian Open, will make his debut in the grass-court tournament.

“I’ve heard so much about this club, so many great champions have lifted the trophy over more than 100 years, and I am looking forward to having my own chance to compete on grass for the title in June,” last week’s Marseille Open winner Tsitsipas said.