The world was watching when Michael Phelps nabbed his 19th Olympic medal for Team USA in London Tuesday night -- including POTUS himself.

On Wednesday, Phelps, 27 -- whose recent victory makes him the most decorated Olympic athlete ever -- discovered a very special message in his Twitter feed from none other than President Barack Obama.

"Congrats to Michael Phelps for breaking the all-time Olympic medal record. You've made your country proud," Obama tweeted.

PHOTOS: Meet Team USA's gymnasts

"Thank you Mr. President!!" Phelps replied. "It's an honor representing the #USA!! The best country in the world!"

Obama followed up his tweet to the swimming champ with a phone call Wednesday, during which he called Phelps "the greatest Olympian ever."

The President also gave Team USA's gold medal-winning gymnasts -- affectionately dubbed the Fab Five -- a ring Wednesday to congratulate them on their stellar performance during the team finals.

VIDEO: Athletes to watch at this year's Games

"Way to nail that vault," Obama told McKayla Maroney. "It was unbelievable."

He had some kind words for the rest of the ladies as well, including fan-favorite Gabby Douglas. "You just tore it up," the President told the 16-year-old. "I know how hard you worked to get there. Keep at it. Stay cool."

This article originally appeared on President Obama Tweets His Congrats to Michael Phelps