Any doubts about Williams being ready to carry off another Major were largely dispelled as she powered to a 6-3 6-4 victory over Germany's Julia Goerges on No.1 Court.
This was a repeat of last year's semi-final, when Williams also won in straight sets, and sets up a fourth-round match for the American against Spain's Carla Suarez Navarro on Tuesday (AEST).
Seven-time Wimbledon champion Williams will hope to remain in the trophy hunt come finals weekend, and the 37-year-old No.11 seed looked in shape to last the distance in London as her serve fired and ground shots invariably found their mark.
All four past meetings had gone Williams's way, without costing her a set, and pressure was on Goerges early on as she grittily saved three break points in the second game of the match.
Serena broke in the sixth game, and clinched the set at the third time of asking by making a forehand winner.
Goerges played at a high level all through the match, albeit landing fewer first serves than she would have wanted.
The 30-year-old from Bad Oldesloe saved three break points with clean winners in game five of the second set, every shot becoming a pint of blood for the battling No.18 seed.
When a fourth break point came along, Goerges floated a backhand wide and Williams had a lead she showed no sign of relinquishing, letting out a shriek of joy when Goerges netted a forehand on match point.
Williams landed 71 per cent of first serves and at that level she is usually unbeatable.
Knee problems that have plagued her season have yet to resurface in London, which bodes well for the challenges ahead.
"It's been an arduous year for me," Williams said. "Every match, I'm hoping to improve tons. Every time I go out there I try. I'm getting a really late start but all that matters is I'm still here."
She has been relishing the doubles union with fellow former Wimbledon champion and home favourite Andy Murray, saying she was so excited by the prospect it might give her "performance anxiety".
Williams added: "I wanted to play mixed because I've played just about 15 matches so far this year so I thought it could really help me."
Serena Williams  bt Julia Goerges  6-3 6-4
Williams – 19/15
Goerges – 17/13
Williams – 7/0
Goerges – 5/2
BREAK POINTS WON
Williams – 2/8
Goerges – 0/0
FIRST SERVE PERCENTAGE
Williams - 71
Goerges - 51
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Williams – 76/71
Goerges – 83/43
Williams - 64
Goerges - 51