Helen Mirren Follows Ex-NFL Star Will Smith on Instagram ... Here's Why

Helen Mirren only follows two people on Instagram -- one of whom is ex-NFL star Will Smith.

The big question ... why???

Smith was shot and killed during a road rage incident in New Orleans last year -- and with Mirren being a social activist, we wondered if she was following Smith to make a point.

So, we asked her about the situation as she left E. Baldi in Beverly Hills on Tuesday with her partner, Taylor Hackford.

Unfortunately, Mirren says the whole thing is a giant mix-up ... but she's very sweet about it.