Serena Williams stayed on track for an eighth Wimbledon title as she fought back to beat Italian Camila Giorgi 3-6 6-3 6-4 in a fiercely contested quarter-final.

For the first time in the tournament the 36-year-old was seriously challenged as unseeded Giorgi fought fire with fire to claim the opening set on Centre Court.

Williams responded by raising the intensity level and began striking the ball with ferocious power to break Giorgi's serve for the first time on her way to levelling the match.

World number 52 Giorgi dropped serve to love early in the decider but hung in gamely to at least make Williams serve to reach her 35th Grand Slam semi-final and 11th at Wimbledon.

Williams stepped up to the line at 5-4 and brought up match point with an ace before completing victory when Giorgi could only push a forehand into the net.

Jelena Ostapenko blasted her way into her first Wimbledon semi-final with a display of power hitting against Dominika Cibulkova.

Ostapenko struck 32 winners to just six from her opponent and won 7-5 6-4 in an hour and 22 minutes to set up a last-four clash against Angelique Kerber.

It was a thoroughly destructive performance from the Latvian, who has already proved her shock French Open triumph last summer was no fluke.

She was the only quarter-finalist from last year to reach the last eight and is now through to her second grand slam semi-final having not dropped a set.

Kerber is through after a straight-sets win over Russian youngster Daria Kasatkina.

The 30-year-old German, a former world number one and the highest-ranked woman left at the championships, battled to a 6-3 7-5 victory on Centre Court.

It is the third time Kerber has reached the last four at Wimbledon, where she was runner-up in 2016.