The Canadian world No. 7 is the highest-ranked men's tennis player to pull out so far, saying Friday: "It is with a heavy heart that I am announcing my withdrawal from participation in the Rio Games."
Raonic represented his country at London 2012, and is a regular member of its Davis Cup team.
"After much deliberation with my family and coaches, I am making this decision for a variety of health concerns including the uncertainty around the Zika virus," the 25-year-old said on his Facebook page.
"This was a difficult, personal choice and I do not wish for it to impact the decision of any other athlete heading to the Games."
Raonic -- beaten by Andy Murray in his first grand slam final
-- is the first top-10 male tennis player to rule himself out of Rio, as the sport makes its eighth Olympic appearance since returning to the schedule in 1988.
Of the other leading men to pull out, French Open semifinalist Dominic Thiem, American world No. 16 John Isner and Spain's No. 20 Feliciano Lopez have decided to play in ATP Tour events instead as these tournaments offer ranking points -- while the Games do not.
Nick Kyrgios made himself unavailable after a dispute with the Australian Olympic committee while fellow top-20 player Bernard Tomic -- who was also criticized by the country's sporting authority -- has decided to play in a Mexican tournament.
The Olympic tennis events have been squeezed into the middle of a heavy August schedule on the men's and women's tours, leading up to the U.S. Open at the end of that month. They will be played on fast hard-courts -- not the clay of February's Rio Open -- so players do not have to adjust.
While the symptoms of Zika -- which include a rash, headaches and joint pain -- are not severe, the virus has been linked to microcephaly in newborn babies and some cases of the muscle-weakening disease Guillain-Barré syndrome in adults.
Many of the world's top golfers -- especially those starting families -- have cited Zika as their reason for missing the Olympics.
The top four men -- Jason Day, Dustin Johnson, Jordan Spieth and Rory McIlroy -- will not be present when the sport returns after a 112-year absence.
Tennis' male No. 1 Novak Djokovic will represent Serbia at the Olympics, according to the official entry list released Friday, though he said at Wimbledon this month he still had concerns about Zika and was seeking more information about it.
Women's No. 1 Serena Williams was listed to defend her Olympic singles and doubles titles.
"I'm going in with a whole mindset of how do I protect myself, how I prevent and also raise awareness for this," the American told USA Today last month before winning her 22nd grand slam crown at Wimbledon.
Former world No. 1 Victoria Azarenka will not feature in Rio, despite being included in the entry list along with Raonic
, having announced Friday that she is pregnant and due to give birth to her first child at the end of this year.
The London 2012 bronze medalist has not played since May's French Open due to a knee injury, but plans to return in 2017.
"I have been truly inspired by so many strong female athletes who return to the very top of their sport after having children, and I plan to do exactly that," the two-time major winner from Belarus, now ranked sixth, said on social media.
"There is nothing more special than becoming a parent, and I'm blessed to have so many examples of women, in every walk of life, who have pursued careers they love while raising children."
Last month, Brazil's new health minister told tourists and athletes that the risk of catching Zika in Rio was "almost zero."
"We are here to put at ease the minds of all residents and tourists coming to the games," Ricardo Barros said at a news conference.
He cited a study by the UK's Cambridge University that concluded there was a very low chance that any of the expected 500,000 foreign tourists would get the virus, which was detected in Brazil last year.