Michael Phelps finished his career in the most Phelps way possible -- by winning a gold medal in the 4x100-meter medley relay.

About 45 minutes later, the 31-year-old took the Olympic podium for the final time and listened to "The Star-Spangled Banner" with his gold medal draped around his neck.

Phelps fought back tears but eventually gave in, which created a chain reaction across the world. Here come the waterworks ...

Many, including a handful of Phelps' teammates, think they'll see him in the pool once again -- possibly at the 2020 Tokyo Olympics.

But if this was Phelps' final goodbye, it was certainly a tearful one.