The World Series bonus checks are in ... and the Houston Astros are coming up BIG!!!!

Here's how it works ... each team in the MLB playoffs gets a bonus check based on how far they advanced. The bonus money is pooled from gate receipts from the playoff games.

The big winner -- the Houston Astros ... with each player getting a $438,901.57 bonus check!!!!

According to MLB, it's the largest bonus ever paid out. The previous record was held by the 2014 SF Giants, which paid players $392k each.