The legendary duo will be involved in the mixed event which takes place between December 29 and January 5 in Perth, Australia.
Team USA will take on Team Switzerland on New Year's Day in 2019 with 23-time Grand Slam champion Serena leading her team against 20-time Slam winner Federer's.
For Serena, it will be her first return to action in Australia since her famous 2017 triumph at Melbourne Park when she was eight-weeks pregnant with her daughter Olympia.
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The 37-year-old will be partnered by rising star Frances Tiafoe, who she is excited about playing with, while Federer will be re-joined by Belinda Bencic.
“I always enjoy playing in Western Australia in front of the crowd at Perth Arena," Williams said. "The Aussie fans are so warm and supportive and the Hopman Cup always gives me a great start to the season, especially ahead of the Australian Open.
“I haven’t played with Frances in mixed doubles before, but have watched him from a far this year. He has a very bright future and I’m looking forward to being on court with him, it will be a lot of fun.”
Germany will once again be represented by world number three Angelique Kerber and world number five Alexander Zverev.
For Australia, Ashleigh Barty and Matt Ebden will hope to delight the home fans, while Cameron Norrie and Katie Boulter will play for Great Britain.

HOPMAN CUP LINE-UP

Australia - [48] Matt Ebden and [19] Ashleigh Barty
France - [19] Lucas Pouille and [39] Alize Cornet
Germany - [5] Alexander Zverev and [3] Angelique Kerber
Great Britain - [78] Cameron Norrie and [109] Katie Boulter
Greece - [15] Stefanos Tsitsipas and [43] Maria Sakkari
Spain - [147] David Ferrer and [15] Garbine Muguruza
Switzerland - [2] Roger Federer and [41] Belinda Bencic
USA - [41] Frances Tiafoe and [17] Serena Williams
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