The Belgian, who will be retiring for a second time after this year's U.S. Open, looked like a pale shadow of the player who has won four major titles. She struggled to get her serve into gear and committed a string of unforced errors.
Kerber was in sparkling form and totally dominated the exchanges against crowd favourite Clijsters, who was suffering from an abdominal injury in the leadup to Wimbledon.
Clijsters survived two match points at 5-0 down in the second set but it was a last throw of the dice against the fiercely determined Kerber who served out for victory.
At least one German player is guaranteed a place in the semi-finals after Kerber booked a last-eight date with compatriot Sabine Lisicki.
Federer shrugs off injury to advance
Roger Federer shook off a back injury to beat Belgium's Xavier Malisse 7-6, 6-1, 4-6, 6-3 and reach the Wimbledon quarter-finals on Monday.
The six-times champion left Centre Court after the seventh game of the first set for treatment and returned eight minutes later before dropping his serve to trail 5-6.
But the third seed broke back immediately, roared through the tiebreak 7-1 and dominated the second set.
The 31-year-old Malisse, world number 75, broke the Swiss early in the third set and with Federer's movement clearly restricted the underdog pulled a set back.
Federer received more off-court treatment and dropped his serve again at the start of the fourth set but Malisse's game suddenly fell apart and the 16-times grand slam champion wrapped up victory with an ace.
flandersnews and Reuter.