Megaceros is a genus of hornworts in the family Dendrocerotaceae. The genus is found in the Old World tropics of east Asia and Australia. Its name means 'big horn', and refers both to the exceptionally large size of the gametophyte thallus and to the large, horn-shaped sporophyte that the plants produce. Many species have a branching thallus that is more than two centimeters wide. The gametophytes are monoicous.