Need at least a tad of info.

Begin with these:
In a pot or the ground?
How long planted?
Watering habits -- how often & how long?

Pictures. too, please.

Wilted tomato is planted in the ground since about first week of April. I water about twice a week from the bottom, just a slow drip from the hose. If soil looks damp down a couple of inches I don't water. Soil is highly amended with compost and organic fertilizer worked in prior to planting, nothing since. Plant was very vigorous.

I am having the exact same problem but now after pulling up a large tomato plant that had wilted, there are 3 more with the same problem. All the plants are already large and with fruit and flowers. It is only the leaves that are wilted.