Glamorgan 168 for 6 (Lloyd 38*) beat Hampshire 105 (Salter 3-34) by 63 runs
Hampshire suffered a Lord's hangover as they were skittled for 105 as Glamorgan got their Vitality Blast campaign off to a one-sided victory.
James Vince's side lifted the Royal London One-Day Cup last week but suffered a humiliating 63-run defeat, collapsing to 34 for 7 at one stage in front of a higher crowd than they normally draw of just over 6,000 fans.
The nature of the defeat was a shock for a county that has been one of the strongest in the country in the shorter formats for many years and the fact that they had finally drawn the sort of crowd they deserve to the Ageas Bowl only to falter at the wrong time must have added to their frustration.
Andrew Salter led the Welsh side's bowling attack taking three for 34 - with Graham Wagg also taking two wickets in Glamorgan's biggest ever format win, by 63 runs.
Hampshire's coach, Craig White, made no attempt to disguise his embarrasssment. "It was bitterly disappointing," he said. "It is a massive wake up call after Saturday. Hopefully this is our blip and every team has one shocker along the way.
"There are some strong teams out there and this makes us realise that everyone is coming for us. We are the team to beat. It was a massive crowd down and they were expecting something after Saturday."
Colin Ingram, Glamorgan's captain, was buoyed by the result. "Salter has opened the bowling for us in the past and he is a big character and likes the challenge," he said. "Fair play to him as the first ball went out the ground and then to get two wickets in the same over was a great comeback.
"We said before the competition we wanted to use it to chance momentum in the group and you can already see the smiles in the group. I feel this is a huge turning point in our season."
Vince had won the toss under stunning sunny skies and elected to bowl before being set an around par 169 to win on a good wicket.
Colin Munro made an immediate impression to the Ageas Bowl crowd as he slapped Salter back over his head for a first ball maximum. But the off-spinner replied by having the destructive New Zealander caught behind and then struck a swinging Rilee Rossouw plumb in front as the collapse started.
Tim van der Gugten then produced an outrageous caught and bowled to dismiss skipper Vince, the fast bowler plucking the return with his right hand.
Sam Northeast followed, pulling straight up into the air, leaving the hosts 12 for four, and then Tom Alsop swept to square-leg.
Lewis McManus and Liam Dawson identically fell pulling to deep-square leg in the same Graham Wagg over.
All-rounders Kyle Abbott and Gareth Berg added 54 for the eighth wicket, and avoided the ignominy of Hampshire's lowest T20 total but it was futile as the latter was lbw to Craig Meschede.
Abbott and Chris Wood were both stumped as Glamorgan eased home with more than three overs to spare.
Glamorgan's innings had started slowly, the first three overs only managing 12 runs, but accelerated throughout to what appeared to be a competitive total.
Afghan Mujeeb Ur Rahman has taken over from veteran Shahid Afridi as Hampshire's overseas mystery spinner, and took little time to cause mayhem with his versatile directions of turn.
The 17-year-old showed his box of tricks with a wicket maiden, as he bowled Australian Usman Khawaja with his third delivery.
Ur Rahman was hit for 19 in his second over, as Colin Ingram tonked him for a trio of boundaries, and eventually posted promising figures of one for 34 on debut.
Shaun Marsh picked out Rilee Rossouw on the mid-wicket boundary as Dawson continued his brilliant white-ball form.
Ingram and Aneurin Donald were both dropped, the former a caught and bowled chance off Abbott, while the latter was put down by Northeast on the point boundary.
And the duo both took their second chances with big hitting contributions to the total with scores of 35 and 26.
Ingram eventually departed when he scooped Dawson, who was the pick of the bowlers with analysis of two for 24, to Ur Rahman at short fine leg before Donald picked out Alsop at long on.
Chris Cooke was lbw to Abbott and Wagg toed a catch to Vince at cover but David Lloyd ended the innings with a flourish with a pair of massive sixes down the ground as he reached an unbeaten 38 from 26 balls.