ANSWER: Three. 

There are three main Scripture readings, the third of which is taken from the Gospel. 

 Of course, besides these three main readings, the words/prayers of the Mass are largely composed of Scripture from start to finish – the responsorial Psalms, the Our Father, the “Holy, Holy, Holy,” the words of the priest during the consecration, the hymns that come directly from Scripture, etc., etc., etc.

Instructions for Mass in the U.S.   Scripture at Mass   Scripture in the Order of the Mass