Gloucestershire 218 for 6 (Klinger 87, Jones 39*, Arafat 3-56) beat Hampshire 217 for 7 (Adams 97, Smith 50) by four wickets
Michael Klinger led from the front as Gloucestershire reached their first one-day semi-final for 11 years with a four-wicket Royal London Cup win over Hampshire at Bristol.
The skipper made 87 off 81 balls, with 10 fours and 2 sixes, to guide his side to a victory target of 218 with six balls to spare, Geraint Jones (39 not out) and Jack Taylor (34) virtually finishing the job with a stand of 44 in only 22 balls after Klinger's dismissal had roused Hampshire's hopes.
Gloucestershire head coach Richard Dawson said: "It was a game that went right to the wire, with so many ups and downs, and the great thing is that we are developing a good habit of getting across the line in close finishes.
"As things stand, Michael flies back to Australia on Friday. There have been talks about the possibility of him playing in the semi-final - or the final if we get there - but nothing has been agreed at this stage and I have no idea whether it will happen."
After rain had reduced the quarter-final to 34 overs per side, Jimmy Adams, with 97 off 99 balls and Will Smith, who smacked 50 off only 25 deliveries, in a late rush of runs that ensured Hampshire's total of 217 for 7 was competitive.
Adams rescued Hampshire from a dreadful start that saw Michael Carberry and Adam Wheater fall in the first two overs of the innings when play finally got underway at 1.45pm, with Gloucestershire having won the toss.
He shared stands of 68 with James Vince (31) and 50 with Liam Dawson (21) before Smith came in to produce a classic one-day cameo, full of improvised strokes, that saw 77 runs scored off the last six overs.
Adams was denied a deserved century when failing to beat Fuller's throw to the wicketkeeper from long-on as he chased a second run having driven Benny Howell.
Smith was dropped twice by Hamish Marshall in the latter stages of his enterprising knock and reached a brilliant half-century off 24 deliveries before Marshall atoned by catching him at long-on off the final ball of the innings.
Off-spinner Jack Taylor was the most economical Gloucestershire bowler with 1 for 30 from his seven overs. But Payne and Howell proved expensive and it was a surprise that slow left-armer Tom Smith was left unused.
Adams had a chance to add to his heroics with the bat when Gloucestershire replied, but could not cling onto a sharp chance diving to his left at point offered by Klinger on nought, off Fidel Edwards.
Chris Dent fell cheaply and Klinger lacked meaningful support as Gareth Roderick, Hamish Marshall and Benny Howell could contribute only 30 runs between them. When Howell fell in the 21st over the scoreboard read 104 for 4 and Hampshire were on top.
While Klinger was there, batting in a class of his own, Gloucestershire retained hope and Jones helped add 59 in 8.1 overs as the skies darkened before Yasir Arafat struck what appeared the key blow in the 29th over.
Aiming a big shot, Klinger skied a catch to cover where Adams held on to the delight of his team-mates. There were still 55 needed off less than six overs.
An expensive over from Edwards followed which saw him concede five wides off the first delivery and three boundaries. With four overs left Gloucestershire required 32, with Jones having been joined by Taylor.
The latter launched Arafat over long-on for two successive sixes and a four as Hampshire's bowling fell apart. When Taylor was out 11 were needed at a run a ball and Jones finished the match with a six over long-on off Arafat.