A five-time Wimbledon winner, Williams made light work of Anna Tatishvili, beating the fellow American 6-1, 6-2 to reach the second round.
Williams, who lost in the second round at the French Open, hit 31 winners and had 16 aces.
Sharapova, fresh off a victory at the French Open, sent British wild-card entry Samantha Murray packing with a 6-1, 6-0 result.
Seeded fifth, Sharapova was perfect in converting all five of her break-point opportunities, while Murray failed to break the Russian's serve in the 58-minute match. Murray also had six double-faults.
The 32-year-old Williams has won 17 major titles in her career but has not fared well in Grand Slams this year, losing in the fourth round at the Australian Open before her early exit at the French Open.
Williams and Sharapova could meet in the quarterfinals.
"I was quite nervous," Lisicki said after being asked how she felt walking back on the court where she lost 6-1, 6-4 last year to Bartoli.
"I played my first Grand Slam final last year and I'm returning to the court where I played it on. That's normal that there are some nerves involved. It's such a special place for me."
After moving on at Wimbledon, the Danish player was asked if she was also moving on with her love life.
Asked again Tuesday about her breakup with fiancé pro golfer Rory McIlroy, she said: "I feel like I've answered that question a lot of times."
However when asked about the possibility of a budding relationship with men's tour player Feliciano Lopez, Wozniacki played coy.
"He's a great guy," she said. "This is very awkward."
No. 13 Eugenie Bouchard, a semifinalist in the last two Grand Slams, also advanced.
Seeded women on the way out were No. 7 Jelena Jankovic, the 2008 U.S. Open runner-up; No. 28 Svetlana Kuznetsova, a two-time major champion who lost to Michelle Larcher de Brito of Portugal 3-6, 6-3, 6-1; and No. 29 Sorana Cirstea, who was beaten 6-4, 3-6, 6-1 by 18-year-old qualifier Vicky Duval of the United States.
Information from The Associated Press was used in this report.