It was their 61st competitive match since 1986 and first meeting at the Crucible Theatre in Sheffield since White enjoyed a 10-4 win in the first round of the 1998 World Championship.
Six-times World Championship finalist White famously lost four of his six Crucible finals to seven-times world champion Hendry between 1990 and 1994, but always looked the likelier winner on this occasion as he set up a final with Ken Doherty, a 4-1 winner against fellow Irishman Michael Judge in the second semi-final.
Northern Ireland Open
Northern Ireland Open 2021 - Draw, schedule, results and all you need to know
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"It is great to see Stephen Hendry practising and playing well again," said White. "He's going to be part of the seniors for the next five or six years. He'll be back trying to get his revenge, make no mistake.
It's always great to beat him because he's such a great competitor, a great battler. Now he's playing well again, it's even more difficult.
"But I'm just trying to win this tournament so whoever stands in front of me, I want to beat.
Hendry made 64 in the second frame on his way to restoring parity at 1-1, but White moved 3-1 up clearly boosted by a superb contribution of 130 in the fourth frame, the highest break of the event.
The Scotsman took the fifth frame despite an early 52 from White, but the Londoner pounced on a missed blue by Hendry with a closing 55 enough to see him over the line.
White will face 1997 world champion Doherty - who made breaks of 60, 85 and 57 in his win against Judge - over the best of nine frames in the final at 7pm with a £25,000 first prize and a place in the Champion of Champions later this year on the line.
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First round results
- Ken Doherty (Ire) 4-3 Rodney Goggins (Ire)
- Patrick Wallace (NI) 2-4 Darren Morgan (Wal)
- Jimmy White (Eng) 4-1 Joe Johnson (Eng)
- Aaron Canavan (Jer) 4-3 Leo Fernandez (Ire)
- Stephen Hendry (Sco) 4-3 Nigel Bond (Eng)
- Wayne Cooper (Eng) 4-2 Gary Filtness (Eng)
- Michael Judge (Ire) 4-1 Dennis Taylor (NI)
- Tony Knowles (Eng) 0-4 Peter Lines (Eng)
- Stephen Hendry (Sco) 4-1 Aaron Canavan (Jer)
- Jimmy White (Eng) 4-1 Peter Lines (Eng)
- Wayne Cooper (Eng) 1-4 Michael Judge (Ire)
- Ken Doherty (Ire) 4-2 Darren Morgan (Wal)
- Stephen Hendry (Sco) 2-4 Jimmy White (Eng)
- Ken Doherty (Ire) 4-1 Michael Judge (Ire)
- Jimmy White (Eng) v Ken Doherty (Ire)
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