AceShowbiz -

Sean Penn has seemingly found a new love following his split from Charlize Theron. According to an eyewitness, the actor of "The Gunman" was seen kissing a 20-something mystery blonde during a romantic date night at a Chicago restaurant on Sunday, March 13.

The source tells PEOPLE, "He came in with no reservation so he was not pretentious or trying to set it up or making sure he was incognito - he literally walked right in." According to the source, "a beautiful young blonde in her 20s," sat with Sean "in plain sight over in the window seat," which the source notes "looks out onto the Chicago River, so it's a pretty romantic view."

The couple reportedly ordered cocktails "oysters, a sea bass and a steak, and then they both had dessert and hot tea." Throughout the meal, "they were very romantic with one another," says the source. After finishing dinner, Sean posed for a photograph with the restaurant's hostess, and when other people began asking for their own pictures, the pair "dashed out the door."

Sean ended his engagement to Charlize following their appearance at Cannes in May 2015. Following the split, the "Milk" actor stepped out with some beautiful ladies. In July 2015, he treated Minka Kelly for an extravagant birthday dinner in Napa, California. In August 2015, he was spotted on a dinner date with Emmanuelle Vaugier at Madeo in West Hollywood.