Scott Disick -- Party All Day and All Night with New Mystery Blonde (PHOTOS)

Scott Disick and a hot leggy blonde put in some hardcore hours -- partying together all over NYC from daytime, into nighttime ... straight into Thursday morning.

Disick and the mystery chick started their party adventure at his hotel ... they were spotted walking out of the Trump Soho Wednesday afternoon. They hit up a bar in the East Village ...then a house party, and eventually 1 OAK Nightclub.

And they still weren't done. The mobile party kept rolling at Soho House ... where they eventually emerged at 6 AM Thursday.

Unclear who the young lady is, but she's the polar opposite of Kourtney Kardashian -- tall, blonde ... and obviously no issues with Scott's party lifestyle.

The lord has risen again.