Morelia spilota is a large species of python in the genus, reaching between 2 to 4 metres (6.6 to 13.1 ft) in length and weighing up to 15 kilograms (33 lb). M. s. mcdowelli is the largest subspecies, regularly attaining lengths of 2.7–3 m (8.9–9.8 ft).[6] M. s. variegata is the smallest subspecies, averaging 120–180 cm (3.9–5.9 ft) in length. The average adult length is roughly 2 metres (6.6 ft). However, one 3-year-old captive male M. s. mcdowelli, measured in Ireland, was found to exceed 396 cm (12.99 ft). Males are typically smaller than females; in some regions females are up to four times heavier.[6] The head is triangular with a conspicuous row of thermoreceptive labial pits.
The colouring of Morelia spilota is highly variable, olive to black with white or cream and gold markings. The patterning may be roughly diamond shaped or have intricate markings made up of light and dark bands on a background of gray or a version of brown.