"Aliens exist, there's no two ways about it," Sharman told the newspaper.
"There are so many billions of stars out there in the universe that there must be all sorts of different forms of life," she said. "Will they be like you and me, made up of carbon and nitrogen? Maybe not."
Sharman became the first Briton in space when she spent eight days as a researcher on the Soviet space station Mir in 1991. She was 27 at the time, making her one of the youngest astronauts in history.
“It’s possible [aliens are] here right now and we simply can’t see them,” she added.
In the same interview, Sharman discussed her experience of looking at the Earth from space, saying there’s “no greater beauty.”
“After take-off we left the atmosphere and suddenly light streamed in through the window. We were over the Pacific Ocean,” she told the newspaper. “The gloriously deep blue seas took my breath away.”
She also expressed frustration with frequent references to her as “the first British woman in space” when she was in fact the first British person overall.
“It’s telling that we would otherwise assume it was a man. When Tim Peake went into space [in 2015], some people simply forgot about me,” she said. “A man going first would be the norm, so I’m thrilled that I got to upset that order.”
Helen Sharman, Britain’s first astronaut, said she believes in extraterrestrial life in an interview with The Guardian published Sunday.