Hasta el final

Hasta el final
 

I know it means untll the end. Can you also correctly say hasta el fin?

Yes, although for me there is a little nuance:
If you say "hasta el fin", it means until the end of everything, but if you say "hasta el final", you mean until the end of a specific situation.
Yet, I think most native speakers use "fin" and "final" as synonyms in this context. :)

Thank you!