Konta, 27, came from a set down to beat world number eight Sloane Stephens before overcoming seven-time Grand Slam winner Williams, now ranked 50th.

Williams was hampered by injury and an assured Konta won in 72 minutes.

She will play Czech teenager Marketa Vondrousova or Russian Daria Kasatkina in the last eight in Rome.

Williams received a bye into the third round after sister Serena withdrew because of a knee injury.

Wiliams, 38, had won her past three meetings with Konta, including the 2017 Wimbledon semi-final.

Williams had her right knee strapped and, although she improved as the match wore on, Konta reached the first Premier clay court quarter-final of her career.