A film unwinding apparatus for a wrapping machine (10) comprises a supporting unit (60) fixable to said wrapping machine (10), and an unwinding unit (50) provided with a reel (3) of film (4) and with roller means (55, 56, 57) for unwinding said film (4) from said reel (3) and winding it around a load (L); the unwinding unit (50) is removably couplable to said supporting unit (60) in an assembled configuration (A); the roller means (55, 56, 57) comprise a first pre-stretching roller (55) and a second pre-stretching roller (56) for unwinding and pre-stretching said film (4) and the supporting unit (60) comprises driving means (70) for rotating the pre-stretching rollers (55, 56) in said assembled configuration (A).