The Oscar winner was aware of the confusion on Twitter after Reeves, 55, appeared at the LACMA Art + Film Gala over the weekend holding hands with artist Alexandra Grant, 46, who bears a resemblance to Mirren.
"I saw that," Mirren told "Entertainment Tonight" on Wednesday at the premiere of her new movie. "That was very flattering on me, you know, because she's obviously lovely."
With her naturally gray hair and bangs, Grant had people doing a quick double take thinking Reeves was with Mirren.
Mirren, 74, has been married for 22 years to director Taylor Hackford, 74, who does have a connection to Reeves in that he directed the "John Wick" star in the 1997 movie "The Devil's Advocate."
"I do know Keanu very well,'' Mirren said. "He did a film with my husband and he is just the most adorable, lovely person. So she's a lucky girl, and I'm sure that he's a lucky boy."
Grant and Reeves also have a long history of working together, as they partnered to launch a small press in Los Angeles called X Artists’ Books, according to The New York Times.
They met at a dinner party in 2009, which was followed by their first book together, "Ode to Happiness,” and then another book, "Shadows," a few years later.
Their possible relationship has also sparked a conversation about age-appropriate dating and then a response about whether a man dating a woman nine years younger than him deserves that designation.
“If the ages were switched and Grant was 55 instead of 46, people would view the situation differently,” Columbia University professor Sharon Marcus told NBC News on Tuesday. “But now Keanu Reeves is getting treated as a king and prince for dating a woman older than 25, because men get graded on a curve and are praised for being moderately decent.”
We can only imagine what the conversation would have been like if Reeves was actually dating Mirren, who is 19 years older than him.
The British legend has shown over the years that naturally aging is beautiful.
“You either die young or you get older. That’s the reality. I don’t want to die young. I never did want to die young. I’m too curious about life,” she told TODAY Style last year. “All lives have their ups and downs. You have two choices. You have to embrace it and allow it to happen. It’s the natural rolling on of life. It happens to every single person on the planet. It’s just a part of being a human being.”