The world number three overcame a second-set fightback from 18th-ranked Bencic to win 6-2 6-7 (2-7) 6-0.

Romania's Halep, 27, will overtake Naomi Osaka at the top of the rankings if she wins the title.

She will play either Kiki Bertens or Sloane Stephens - who she beat in last year's French Open final - on Saturday.

Halep has reached the Madrid final four times in her career and won the title in 2016 and 2017.

Bencic, who beat Japan's Osaka in the quarter-finals, had won her past two meetings against Halep.

However, Halep, who describes clay as her favourite surface, was dominant in the final set.