Michael Douglas -- TRAVELIN' SOLO ... After Separating From Catherine Zeta-Jones

Sportin' a fresh suit, some fancy shoes and a bachelor mind-set, Michael Douglas caught a flight in France yesterday ... just days after reports surfaced that he separated from his wife.

68-year-old Douglas and 43-year-old Catherine Zeta-Jones haven't been photographed together since April -- fueling speculation the two are calling it quits on their 13-year marriage.

As for Catherine, she's reportedly been hangin' in New York with the couple's 2 kids.

No word on where Douglas was headed yesterday -- but that's a pimp suit, right?