Southampton manager Ralph Hasenhüttl was left to rue missed opportunities as his side fell to just a second home defeat of the season at the hands of Newcastle.
Saints took the lead midway through the first half when Stuart Armstrong headed home, only for Chris Wood to level it up before the break.
The comeback was completed on 52 minutes when Bruno Guimarães cleverly flicked beyond Fraser Forster, with sustained pressure from the hosts failing to produce an equaliser in response.
Reflecting on a frustrating evening, Hasenhüttl said: “It was not necessary that we lose this game today. We had enough opportunities to score today. We had good chances.
“It was tough against a deep defending opponent and when you concede two easy goals, it’s always tough. But in the end, we haven’t been clinical enough.
“They didn’t have a lot,” he continued. “We couldn’t take these opportunities and in the moment, it’s a little bit harder because we don’t score these goals and concede easy ones and it makes it difficult to win.
“We had chances, massive chances, where we can score and we didn’t today. This is our fault and we have to do it better.”