The 23-year-old from King City, Ont., won Canada's first gold medal at the London Games on Saturday with a victory on the women's trampoline.
Messages of support soon followed on social media, including congratulations from two famous fans.
"CANADA!!!! We love our trampolines!!," tweeted Canadian music star Justin Bieber. "Congrats to @RosieMacLennan on GOLD!! #ProudCanadian."
Even American movie star Samuel L. Jackson, who has been tweeting extensively throughout the Games, noticed MacLennan's accomplishment.
"BTW, a Big Shout Out to the MUTHACANUKIN Gold Medal Trampoliners!!," Jackson posted.
MacLennan thanked both celebrities on Twitter for the recognition, adding in her reply to Bieber: "It's an unreal feeling hearing the national anthem & an honour to represent Canada in something I love!"
In other tweets from Canadian athletes at the Games:
— Soccer player Melissa Tancredi posted a message ahead of Canada's semifinal game against the U.S. on Tuesday: "Time for a Lil training sesh in Manchester. Oh and #neymar and #thiagosilva just showed up at our hotel. Life is but a dream, so thankful."
— Marathon runner Reid Coolsaet posted: "About to watch the Women's Olympic marathon. This should be a great race, and I get to see how the course runs for next Sunday."
— After finishing fourth in the women's trampoline, Karen Coburn spent some time enjoying the sights: "Great day with my family in London! Boat cruise, London eye, tower bridge, and saw part of the marathon. #amazingathletes."
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