WILL SMITH WALKS IN ON JADA, MARC ANTHONY

A suspicious Will Smith paid a surprise visit to Jada Pinkett Smith and found her with Marc Anthony  ... this according to a new report.

In Touch Weekly claims in early August Will had become increasingly suspicious that his wife was having an affair with her "HawthoRNe" co-star Marc Anthony and secretly flew home from a movie shoot -- and if you saw "HawthoRNE," you'll understand why.

The mag claims Will walked in the house, found Marc Anthony and Jada together and left the house crying.