How fast can you get your 401k money out?

I understand that there are certain regulations and restrictions surrounding the withdrawal of funds from a 401k plan. But I'm curious, how quickly can one typically access their 401k funds if they need to? Are there any expedited processes or circumstances that would allow for a faster withdrawal? It's important for me to know this information as I'm considering my financial options and want to make sure I have a clear understanding of the timeline involved.