Books printed in Europe before 1501 are known as incunables. Many of the works that appeared in print before 1501 were religious (e.g. missals) or academic. The majority of texts were in Latin. According to the French Wikipedia article incunable,
Des 30 000 incunables répertoriés, 21 000 sont écrits en latin, 3 000 sont en allemand, 2 000 sont en italien et 1000 sont en français.
Of the 30,000 incunabula inventoried, 21,000 are written in Latin, 3,000 are in German, 2,000 are in Italian and 1,000 are in French.
The English, French and German Wikipedia articles about incunables don't say all that much about the genres that were printed. For example, I have not been able to find when a play was printed for the first time. Presumably, that would have been a Latin or Greek text from Antiquity (unless it was some popular Medieval play).
My question now is: what was the first play that appeared in print in Europe? Who was its author? Where and by whom was it printed? Was it even printed before 1501?