TMZ Sports has learned ... the lucky individual secured the bag on Thursday, earning over 700 times the amount of cash he put down.

A rep for BetUs -- the online sportsbook where the winning ticket was played -- tells us they don't release their customers' names, so the identity of the winner remains a mystery.

The sportsbook says the guy bet on 6 teams to win moneyline -- meaning he had to pick a winner outright -- and the rest of his picks were on "over/under" bets or totals.

His bets were as follows:

San Diego Padres, Milwaukee Brewers, Philadelphia Phillies, St. Louis Cardinals, New York Yankees and the Los Angeles Angels moneyline.

The over/under or totals were Reds-Padres (Over 8), Pirates-Brewers (under 7½), Rockies-Phillies (over 7), Nationals-Marlins (under 8) Braves-Cubs (under 8½), and Yankees-Orioles (over 8½).

BetUS exec Tim Williams tells us, "Believe it or not, we really do love to see our valued customers hit big payouts -- and this young man from Lakewood, WA sure knows how to pick some winners!"

Williams says he hasn't spoken to the man who won the $200K, but he "hopes he has a great summer" with his new fortune.