I recently wrote an article about long films, so here is a list of every film over 4* hours in length that I could think of.
To the best of my knowledge, these were released theatrically around the time of original release (even if at film festivals or just one screening) or had a theatrical release and then later released an extended cut on home media. Basically: all of these were shown in theatres in some form when first released and all of these exist in a version over 4 hours in length.
I'm excluding films that played only at art galleries. I'm also excluding TV series that were later released in film form on home media.
Suggestions and corrections welcome.
* - technically the shortest film here is 3hr54m, to give some leeway to the not-always-accurate Letterboxd listed runtimes