Five top-20 players will challenge Andy Murray for the Aegon Championships crown at Queen's Club in June.
Murray won his third title at the West Kensington club 12 months ago before going on to lift the Wimbledon trophy.
Marin Cilic, the 2012 champion and the man Murray beat in the final last year, returns and will be a danger as one of only six men to have won two titles already this season.
Other newly-announced names include former world number one Lleyton Hewitt and crowd-pleaser Ernests Gulbis, who has made big strides this year.
The entry list is headed by world number six Tomas Berdych, although Murray could go into the tournament as the highest-ranked player with a strong performance over the next six weeks.
Jo-Wilfried Tsonga, Grigor Dimitrov, Kevin Anderson and Gulbis are the other top-20 entrants for the tournament, which starts on June 9.
This year's edition also marks the debut for tournament director Ross Hutchins, who took over from new ATP head Chris Kermode in May.
Hutchins said: "The Aegon Championships player entry list includes current champions such as Andy Murray, established stars like Lleyton Hewitt and exciting young talent in Grigor Dimitrov, Ernests Gulbis and Dominic Thiem, among many others.
"They will compete for a trophy at the Queen's Club that has been lifted in the Open era by Rod Laver, John McEnroe, Boris Becker and Pete Sampras. We can't wait for the tournament to get under way."