Sussex went down to an agonising nine-run Royal London Cup loss at the Ageas Bowl after recovering from an early collapse thanks to David Wiese's stunning 171.
The loss for Ben Brown’s men leaves them third in the South Group, with two games to go.
Hundreds from Aiden Markram (130) and Tom Alsop (124) put the hosts in a strong position as Hampshire reached their fifth highest List A score of 355/5.
Sussex collapsed to 103/5 early on but a 232-run partnership from Wiese (171) and Brown (64) got Sussex close before both were dismissed, and Hampshire wrapped up the tail.
Hants v Sussex - all the pictures
Hampshire captain Sam Northeast won the toss and Tom Alsop and Aneurin Donald began with a 74-run partnership.
Sussex got their first wicket when Donald was caught by Phil Salt off the bowling of Beer for 41. This brought Aiden Markram in with Alsop, and they put on 184 for the second wicket.
Sussex had a few chances to break the stand, Alsop almost being run out on 98 before going on to make his hundred off 116 balls. Markram was also lucky, flashing an edge inches wide of Brown behind the stumps in the same over.
Alsop went for 124 as he tried to hit Briggs for six down the ground but instead he found Garton on the boundary. Rilee Rossouw joined Markram and a few overs later the South African overseas player brought up his hundred off 73 balls. The pair soon made a 50-run partnership, but it was ended when Rossouw chopped onto his stumps attempting to ramp Hamza over the keeper.
Hampshire lost two quick wickets as James Fuller went quickly as Sakande took a catch off his own bowling to dismiss him for six. Then Markram was bowled by Hamza to end his knock of 130. Northeast came to the middle to join Dawson and the pair closed out the innings for the hosts as they finished on 355/5.
In response, Sussex started aggressively with Luke Wright and Salt taking 14 off the first over from Kyle Abbott. Abbott got his revenge in his next over when he bowled Wright for three with a ball that nipped back.
Salt was joined by Garton as the pair looked to rebuild from their early loss. They added 30 before Salt was caught at extra cover by Donald off Gareth Berg to leave Sussex at 52 for two. The situation worsened for Sussex as they lost two quick wickets with Garton out lbw to Dawson for 18 before Harry Finch was caught by Crane off Fuller to leave Sussex at 74/4.
Laurie Evans and Wiese put on 29 before Dawson deservedly got his second when he bowled Evans for 21 to leave Sussex at 103/5. Wiese and Brown then turned the game around for as they put on a stand of 232 for the sixth wicket – the highest for Sussex in List A cricket. Wiese the main culprit of the damage as he scored his highest List A score of 171.
Sussex needed just 21 from the final three overs before Brown was caught by Dawson off Crane for 64. Beer joined Wiese and despite his heroics, he could not carry Sussex to victory as he was caught by Crane in the deep off Abbott. Briggs then was out first ball, scooping a catch to Berg at fine leg to leave Sussex needing 10 off the last over.
Crane held his nerve in the final over as back-to-back stumpings saw off Beer and Hamza as Hampshire continued their strong title defence.
Sussex next host Gloucestershire - that's at Eastbourne on Sunday, 11am start.