Williams, who is 37 years old, made her Wimbledon debut in the same month that Ostapenko was born.
Williams is getting better as the tournament progresses and the quality of opposition supoosedly steps up - she has not dropped a set in her last three matches at SW19. The German whose form seemed to have picked up in the last two weeks of competition, failed to take control after winning the first set.
And Williams ruthlessly seized her opportunity, holding at love to progress to the semis in ominous fashion.
Kerber, who was beaten in three sets, said: "I was really surprised that I was playing on Court Number Two".
Konta, the sixth head of the series, has taken the measure of the French Caroline Garcia 7-6 (3), 4-6, 6-4 on the field # 1.
Rybarikova also beat third-seeded Karolina Pliskova in the second round. She won lots of matches.
And Venus looks on course to reach her first SW19 final since 2009 after sailing past Konjuh into the quarter-finals. The last time that the American tennis player won a title was nine years ago, and it sounds like she is determined to secure one more before she gets too old.
Williams is working towards her 6th Wimbledon title and now holds a 86-14 winning record at the tournament. Roger Federer brushed aside Grigor Dimitrov 6-4, 6-2, 6-4 to qualify for his 50th Grand Slam quartefinal.
Muller, from Luxembourg, advanced to the fourth round for the first time in 10 appearances at the All England Club with a 7-6 (4), 7-5, 6-4 victory. She has yet to advance past that stage.
Experience triumphed over youth on Centre Court as Venus downed Croatian teenager Ana Konjuh 6-3 6-2 in a fourth-round battle of the baseliners.
Key moment: This match was relatively even until early in the second set, when the wheels came off for Konjuh.
The Spaniard dispatched Kerber in a high-quality tussle Monday with fill-in coach and 1994 Wimbledon champion Conchita Martinez looking on.
Halep reached the semifinals at the All England Club in 2014 and played in the quarterfinals previous year.
The match will resume not before 1 p.m. on the same court on Saturday. Novak Djokovic is third. The veteran suggested starting play on the two main show courts before 1pm to get another women's match on the bill.