The Dutchman succeeded David Moyes as United’s permanent manager in the summer and despite an uneven campaign, they have put themselves in position to finish in the top four of the Premier League.
Neville believes they will complete the job – and that even if they miss out, sacking Van Gaal would be the wrong move.
“Absolutely not, he shouldn’t be sacked,” he told talkSPORT.
“It would be a terrible season for Man United and Louis van Gaal (if they do not finish in top four). He would probably say it was a big failure because he knows his job this season. He has to get in the Champions League.
“But on the other hand, if he didn’t, you can’t just sack a manager one year and then sack another manager the year after. Where do you go from there?
“There has to be a level of continuity. I absolutely believe this time there will be continuity and they will stand by him even if he doesn’t finish in the top four – and that’s the right thing to do.”
United have most of their rivals for European qualification still to play before the season finishes and Neville added: “I still think Manchester United will finish in the top four. I think they will scrape in.
“There is a period in March where they have Arsenal in an FA Cup quarter-final, then they have Spurs the Sunday after and Liverpool after that. There is an international break and then they have got Aston Villa, Man City and Chelsea. I’d like to think these games will inspire some of the bigger players at Man United.”