The actress, who is seven years older than her husband Greg Wise, insisted that she is not a "cougar".
She said at the Harper's Bazaar Women Of The Year Awards: "I don't get it. It seems predatory and I don't really approve."
Thompson added to The Daily Telegraph that she would never be interested in dating a significantly younger man.
She explained: "It's easy to be flattered, but I am no cougar. I've had a lot of male attention here from budding young actors asking about getting on in showbusiness.
"One even asked me how to change his agent. It got me thinking about the cougar thing. I am a happily married woman, but, even if I was single, I wouldn't be up for it."