Derbyshire have won the toss and have opted to bowl first.
The visitors are forced into a change as T20 captain Shan Masood has been called up for the Pakistan Test squad in Sri Lanka - and will also miss Finals Day, should they make it. Harry Came comes in.
Somerset are unchanged from the team who won by 47 runs against group winners Surrey last Sunday.
Somerset: Abell (capt), Banton (wk), Smeed, Rossouw, Lammonby, Gregory, Green, van der Merwe, C Overton, Davey, Siddle.
It is now 18 years since Somerset celebrated their one and only Twenty 20 trophyImage caption: It is now 18 years since Somerset celebrated their one and only Twenty 20 trophy
Somerset hold the record for the most appearances in a final - five.
Four times runners-up - in 2009, 2010 and 2011 and again last year - but only one triumph, against Lancashire at The Oval way back in 2005.
Victory tonight would take the Cider Boys to Finals Day for the eighth time - but they face a Derbyshire side much improved this season under Mickey Arthur.
Derbyshire were the last of the 18 counties to make it to a Finals Day in 2019 when they were well beaten by eventual winners Essex in the second semi.
They then finished bottom of their group in 2020, winning just once in 10 games, then second bottom in 2021, when they won only four times in 12 matches.
But what a contrast this season. Nine wins in 14 matches to finish joint level in the North Group on 18 points with Birmingham Bears and Lancashire.
Only an inferior run-rate relegated them to third in the final table - and therefore having to travel to Taunton tonight, instead of enjoying the advantage of a home tie for a top-two finish.
Getty ImagesCopyright: Getty Images
Derbyshire have enjoyed their best season in T20 cricket in 2022, with nine wins from 14 matchesImage caption: Derbyshire have enjoyed their best season in T20 cricket in 2022, with nine wins from 14 matches
Good Evening and Welcome from Taunton
Somerset v Derbyshire Falcons (18:30 BST)
Hello again - and welcome back for the fourth and last of this week's T20 Blast quarter-finals.
There is one more place up for grabs at Finals Day in Birmingham next Saturday night.
We have so far seen one last-ball thriller this week, that astonishing win for Yorkshire over Surrey at The Oval on Wednesday night, followed by sucessive strolls in the sunshine for Hampshire, at Edgbaston, and Lancashire, at Old Trafford.
Rex FeaturesCopyright: Rex Features
Now we move on to the County Ground at Taunton, where Somerset meet Derbyshire.
One of them, by the end of the evening, will have booked their place in next Saturday's second semi-final.
Will it be a Somerset-Hampshire semi for the second successive season? Or will it be only a second Finals Day in 20 seasons of trying for unfancied Derbyshire?
Live Reporting
Ged Scott
All times stated are UK
Tonight's Teams
Somerset v Derbyshire Falcons (18:30 BST)
Derbyshire have won the toss and have opted to bowl first.
The visitors are forced into a change as T20 captain Shan Masood has been called up for the Pakistan Test squad in Sri Lanka - and will also miss Finals Day, should they make it. Harry Came comes in.
Somerset are unchanged from the team who won by 47 runs against group winners Surrey last Sunday.
Somerset: Abell (capt), Banton (wk), Smeed, Rossouw, Lammonby, Gregory, Green, van der Merwe, C Overton, Davey, Siddle.
Derbyshire: (capt), Reece, Guest (wk), Madsen, Cartwright, du Plooy, McKiernan, Hughes, Watt, Aitchison, Scrimshaw.
Officials: Neil Mallender, Ben Debenham, Paul Baldwin, Peter Such.
How do they match up tonight?
Somerset v Derbyshire Falcons (18:30 BST)
Somerset hold the record for the most appearances in a final - five.
Four times runners-up - in 2009, 2010 and 2011 and again last year - but only one triumph, against Lancashire at The Oval way back in 2005.
Victory tonight would take the Cider Boys to Finals Day for the eighth time - but they face a Derbyshire side much improved this season under Mickey Arthur.
Derbyshire were the last of the 18 counties to make it to a Finals Day in 2019 when they were well beaten by eventual winners Essex in the second semi.
They then finished bottom of their group in 2020, winning just once in 10 games, then second bottom in 2021, when they won only four times in 12 matches.
But what a contrast this season. Nine wins in 14 matches to finish joint level in the North Group on 18 points with Birmingham Bears and Lancashire.
Only an inferior run-rate relegated them to third in the final table - and therefore having to travel to Taunton tonight, instead of enjoying the advantage of a home tie for a top-two finish.
Good Evening and Welcome from Taunton
Somerset v Derbyshire Falcons (18:30 BST)
Hello again - and welcome back for the fourth and last of this week's T20 Blast quarter-finals.
There is one more place up for grabs at Finals Day in Birmingham next Saturday night.
We have so far seen one last-ball thriller this week, that astonishing win for Yorkshire over Surrey at The Oval on Wednesday night, followed by sucessive strolls in the sunshine for Hampshire, at Edgbaston, and Lancashire, at Old Trafford.
Now we move on to the County Ground at Taunton, where Somerset meet Derbyshire.
One of them, by the end of the evening, will have booked their place in next Saturday's second semi-final.
Will it be a Somerset-Hampshire semi for the second successive season? Or will it be only a second Finals Day in 20 seasons of trying for unfancied Derbyshire?
Stay with us and find out.