Five-time champion Venus Williams reached the Wimbledon semi-finals for the first time since 2009 with victory over Kazakhstan's Yaroslava Shvedova.
Eighth seed Williams - the oldest Grand Slam semi-finalist for 22 years at 36 - beat unseeded Shvedova 7-6 (7-5) 6-3.
An all-Williams final remains possible after top seed Serena beat Russian Anastasia Pavlyuchenkova 6-4 6-4.
Serena will play Elena Vesnina or Dominika Cibulkova and Venus takes on Angelique Kerber in Thursday's semis.
Germany's Kerber, the fourth seed, beat Romanian fifth seed Simona Halep 7-5 7-6 (7-2) in the opening match on Centre Court.
Unseeded Russian Vesnina takes on Slovakian 19th seed Cibulkova in the remaining quarter-final.