How many plays did Shakespeare write?

William Shakespeare is believed to have written at least 37 plays, as well as a collection of sonnets which remains widely read today. However, it is possible that Shakespeare wrote more plays than the ones we know about today. There are several plays which no longer exist but which are mentioned in other texts, and which many historians believe to be "lost" Shakespeare plays. Remember also that the concept of authorship was different in this period, and collaboration, between multiple writers and between writers and actors, was common. It is very likely that Shakespeare also contributed to other plays, most notably "The Book of Sir Thomas More," for which he was only one of several authors.
The First Folio of Shakespeare's works was collected by his friends shortly after he died and contains 36 plays. It was this folio which first separated Shakespeare's works into histories (such as Henry V and Richard III), comedies (such as Much Ado About Nothing and Twelfth Night) and tragedies (such as Othello and King Lear).