The question is, what and how much do you eat. In general you should wait 1-2 hours, but everyone is different. So you have to find it out what's good for you. If you just do running, you also can just eat a banana and drink some water and start.
But the more protein and fat you eat ( also long carbs), the longer you should wait.
I usually workout in the morning before I've eaten anything.
Minimum 4 hours , depends upon how fast your metabolism is ..
Usually an hour or two but obviously depends on your metabolism