Just hours after Robby Ginepri's 6-4 1-6 5-7 6-4 6-2 defeat by Argentina's Diego Hartfield condemned the U.S. men to their worst showing at Roland Garros in at least 40 years, Williams lit up a dank court one with a 206 kph thunderbolt.
The milestone, a shade slower than Brenda Schultz-McCarthy's overall record of 209 kph hit in qualifying in Cincinnati last July, made up for an otherwise unimpressive 6-1 7-6 second-round victory over fellow American Ashley Harkleroad.
"I loved it. I lost my focus a little bit because I saw the 206," said Williams, who had let slip a 5-1 lead in the second set.
"I was so excited because I broke my record."
The five-time slam champion cannot afford such lapses in the next round as she will be up against in-form Serbian fourth seed Jelena Jankovic.
The last of nine U.S. male competitors to fall in Paris, Ginepri's exit also meant that for the first time in 34 years no American men reached the second round of one of the four majors.
World number ones Roger Federer and Justine Henin did not let the now familiar sight of umbrellas peppered across the stands distract their title charge.
Federer withstood a late fightback from plucky French wildcard Thierry Ascione for a 6-1 6-2 7-6 victory and Henin steamrollered Austrian Tamira Paszek 7-5 6-1.
Wimbledon champion Amelie Mauresmo began a 13th tilt at winning her home grand slam with a 6-0 7-5 triumph over American Laura Granville.
Maria Sharapova showed there was no room for sentiment when she led a batch of Russians into the second round.
Playing
Sharapova made light of her own patched-up shoulder as she powered to a 6-3 7-6 victory. She was joined in the last 64 by 2006 runner-up Svetlana Kuznetsova and ninth seed Anna Chakvetadze.
'BIG COW'
Kuznetsova avenged one of the most painful defeats of her career when she blew fellow Russian Ekaterina Bychkova off court 6-0 6-3.
The third seed was humiliated by Bychkova at the 2005 U.S. Open when she became the first defending champion to lose in the opening round.
Fast forward two years and Bychkova felt the full force of Kuznetsova's wrath.
The roller-coaster careers of another pair of Russians, former champion Anastasia Myskina and 22nd seed Marat Safin, took a further nosedive.
Making her comeback after foot surgery in January, Myskina was embarrassed 6-1 6-0 by American Meghann Shaughnessy.
Myskina, the first Russian woman to lift a grand slam title when she triumphed here in 2004, almost skipped the tournament.
She probably wished she had missed her flight out of Moscow because she has not won a match since last August.
"I have to be a realist. I knew I was not going to win but I just wanted to see how my foot would feel," Myskina told reporters. "You can see I'm moving like a big cow now."
Former world number one Safin raged, rolled in the red dirt and smashed a racket but his histrionics could not prevent a 6-4 6-4 7-5 mauling by Serb Janko Tipsarevic in the second round.