Alexander Rossi says there was 1 very unforeseen consequence to winning the Indy 500 ... a gaggle of women SLIDING into his Instagram DMs ... wanting to hook up!!
TMZ Sports talked to the 2016 Indianapolis 500 winner -- who's 24 and single -- in L.A. Monday ... and asked if his lady situation has changed since winning one of the world's biggest races.
The answer ... a resounding YES!!
Check out the clip!