Halep, who has won the tournament for the last two years, had looked unbeatable on her way to the last eight, dropping nine games in three matches including Wednesday's victory over Pliskova's twin sister Kristyna.
Karolina Pliskova achieved a first with her win over Simona Halep, getting her first tour level win over the World No. 1 to book her spot in a second straight semi-final on the clay this season.
It was sixth seed Pliskova's first claycourt victory over Halep and it was the kind of authoritative performance that will turn a few heads as the French Open looms later this month.
She found her feet at the start of the second set and fought gamely to the end, saving four match points while serving in the final game before netting a routine forehand to cough up a fifth and conceding the match with a tame double fault.
A further break followed in the seventh game of the second set which proved key to her eventual victory. "I'm not stressing myself about this busy schedule". "Despite a slow start, I was still very positive". There is no pressure.
"To see six of the world's top 10 players on our entry list before you even get to the names Andy Murray, Stan Wawrinka, Milos Raonic, Feliciano Lopez, Nick Kyrgios and the British number one Kyle Edmund really whets the appetite for a fantastic week of Tennis", said tournament director Stephen Farrow. I never thought I would beat her.
Bertens had 21 winners and 34 unforced errors and Maria failed to match those numbers, hitting 18 winners and 37 errors, fading from the court in the second half of the match after a great defense and anticipation from Kiki.
Edmund had lost in five sets to Goffin when they last met, also on clay, in the 2015 Davis Cup but the 23-year-old's rise has been sharp since then and this was a completely different contest.
"I believe I can win the match, but I always expect a tough one". She also won in Hobart earlier this year and reached the Australian Open semifinals, where she lost to eventual champion Caroline Wozniacki.
Aside from Nadal and five others from the present top 10 the tournament is likely to see Britain's two-time Wimbledon champion Andy Murray - a five-time victor of the Queen's title - play as he makes a comeback after hip surgery.
Djokovic, recently back from injury, is now under-ranked at 12th.
He will play Austria's Dominic Thiem on Friday for a place in the last four.