Mahathwar is a village in Ghanshyampur tehsil in district of Darbhanga, Bihar, India. As per the data provided by Census of India in 2011, total population of Mahathwar was 4,523 which includes 2,335 males and 2,188 females. Mahathwar covers 353.11 ha area. Pincode of Mahathwar is 847427.