The 22-year-old Russian beat Pole Robert Kubica to the last seat on the grid following an impressive performance at the Abu Dhabi Pirelli tyre test at the end of last season.
“To say I’m happy and proud to join such a famous team like Williams is an understatement,” Sirotkin said.
“It took a huge amount of work to get where I am, and I’m really happy and thankful to everyone involved.
“The result of our combined efforts has helped me achieve my dream, and rest assured the team can rely on me to deliver my best.”
Sirotkin will partner 19-year-old Canadian Lance Stroll, but how does the rest of the grid shape up?
Take a look through the gallery above to find out!