Raducanu beaten by Boulter in all British semi at Nottingham
Boulter won 6-7 (13-15), 6-3, 6-4 in a match held over from Saturday because of bad light after Raducanu had taken the first set in a marathon tie-break.
But Boulter will not have long to enjoy this win, with the British number one back on court later Sunday to face Karolina Pliskova of the Czech Republic in the final of this grass-court warm-up event for Wimbledon.
Boulter, who earlier on Sunday was the only female tennis player named in the British team for the Paris Olympics, eventually proved too strong for Raducanu in a match that lasted more than three hours.
But Raducanu, coming back from a seven-week lay-off as she manages her return from wrist and ankle injuries, could take some heart from her first semi-final since she stunned the tennis world by winning the 2021 US Open as a qualifier.
Boulter paid tribute to Raducanu by saying: "What a match, what an incredible player.
"She is only going to get better and better, she makes it so tough to close it out," added Boulter, 30 in the world rankings, after again reaching the final of her home event.
Former US Open and Wimbledon finalist Pliskova, the 2016 champion and yet to lose at Nottingham, beat France's Diane Parry 6-7 (9-11), 6-1, 6-4 in a semi-final earlier on Sunday.
Victory saw Pliskova, 32, into her first grass-court final since losing to Australia's Ashleigh Barty in the 2021 Wimbledon showpiece match.