Sometimes — with care
A small spoon of plain, unsweetened yogurt is usually tolerated and lower in lactose than milk — but it’s a treat, not a need, and never give yogurt sweetened with xylitol.
Plain yogurt is interesting for cats because the fermentation reduces its lactose, so many lactose-sensitive cats handle a little yogurt better than they handle milk. It offers some protein and calcium and live cultures. But cats gain little nutritionally from dairy, and the usual cautions apply: keep portions tiny, avoid flavoured or sweetened yogurts (sugar, and possibly xylitol, which is dangerous), and stop if it causes loose stools.
No more than a teaspoon of plain natural or Greek yogurt occasionally. Full-fat plain with no additives is best. If your cat is diabetic, overweight or gets diarrhoea from dairy, skip it. It can be a handy way to give a tiny bit of medication.
Related: Can cats drink milk? · Can cats eat cheese? · Can dogs eat yogurt?
General information, not veterinary advice. If your pet has eaten something potentially harmful or shows symptoms, contact your vet or an emergency clinic immediately. Full disclaimer.