Could be a lot of things. Sudden wilting like this usually is root damage, whether physical or disease.

Here Is a closer photo.

Well it still looks like its alive, just seems to need watering. Clip off the dead leaves and leave room for new ones.

It's possible that it's bacterial wilt. Have you noticed any cucumber beetles around?

Rodney

I would agree with theforgottenone1013

it's all to common an issue.

Particularly when one plant wilts and the one next to it is still sound. So far.

No I'm not sure what cucumber beetles are. And I water that plant a lot! I know cukes need a lot of water!