Milos Raonic and Nick Kyrgios will compete in the Aegon Championships at Queen's Club this summer.
They join the already confirmed Andy Murray, Rafael Nadal and Stan Wawrinka for the tournament from 13-19 June.
Canadian Raonic, 25, is second in the ATP Race to London standings for 2016, having reached the semi-finals at the Australian Open and Indian Wells.
"I believe I can do better than I've ever done before on grass," said 2014 Wimbledon semi-finalist Raonic.
"Grass is a surface where I have had some of my best results and I believe I can make an impact at Queen's and Wimbledon this year."
Australian Kyrgios broke into the top 20 for the first time in his career this week, beating Raonic in the Miami Open quarter-final.
"Grass courts are my favourite surface," said the 20-year-old.
"The conditions are perfect, all the Australians have played well there over the years and I'm pumped to be coming back."
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