The fur of clouded leopards is of a dark grey or ochreous ground-color, often largely obliterated by black and dark dusky-grey blotched pattern. There are black spots on the head, and the ears are black. Partly fused or broken up stripes run from the corner of the eyes over the cheek, from the corner of the mouth to the neck, and along the nape to the shoulders. Elongated blotches continue down the spine and form a single median stripe on the loins. Two large blotches of dark dusky-grey hairs on the side of the shoulders are each emphasized posteriorly by a dark stripe, which passes on to the fore leg and breaks up into irregular spots. The flanks are marked by dark dusky-grey irregular blotches bordered behind by long, oblique irregularly curved or looped stripes. These blotches yielding the clouded pattern suggest the English name of the cat. The underparts and legs are spotted, and the tail is marked by large irregular paired spots.
They weigh between 11.5 and 23 kg (25 and 51 lb). Females vary in head-to-body length from 68.6 to 94 cm (27.0 to 37 in), with a 61 to 82 cm (24 to 32 in) long tail. Males are larger at 81 to 108 cm (32 to 43 in) with a 74 to 91 cm (29 to 36 in) long tail. Their shoulder height varies from 25 to 40 cm (9.8 to 16 in).
Their legs are short and stout, with broad paws. They have exceptionally long, piercing canine teeth, the upper being about three times as long as the basal width of the socket. The upper pair of canines may measure 4 cm (1.6 in) or longer.
Clouded leopards are native to Indochina, Thailand, Peninsular Malaysia, Myanmar, Bhutan, Bangladesh, India, and Nepal. They are regionally extinct in Taiwan, and occur marginally in mixed-evergreen forests of the northeastern and southeastern parts of Bangladesh. In the Himalayan foothills of eastern India, they have been recorded up to an altitude of 1,450 m (4,760 ft). They have been reported from relatively open, dry tropical forest in Myanmar and Thailand. They prefer open- or closed-forest habitats to other habitat types.
In Assam, they have been observed in forests, but have not been recorded in protected areas.They occur in northern West Bengal, Sikkim, Arunachal Pradesh, Manipur, Meghalaya, Mizoram, Nagaland, and Tripura.
Clouded leopards are the most talented climbers among the cats. In captivity, they have been observed to climb down vertical tree trunks head first, and hang on to branches with their hind paws bent around branchings of tree limbs. They are capable of supination and can even hang down from branches only by bending their hind paws and their tail around them. When jumping down, they keep hanging on to a branch this way until the very last moment. They can climb on horizontal branches with their back to the ground, and in this position make short jumps forward. When balancing on thin branches, they use their long tail to steer. They can easily jump up to 1.2 m (3.9 ft) high.
Clouded leopards have been observed to scent mark in captivity by urine spraying and head-rubbing on prominent objects. Presumably such habits are used to mark their territory in the wild, although the size of their home ranges is unknown. Like other big cats, they do not appear able to purr, but they otherwise have a wide range of vocalizations, including mewing, hissing, growling, moaning, and snorting. Apart from information stemming from observations of captive clouded leopards, little is known of their natural history and behavior in the wild. Early accounts depict them as rare, secretive, arboreal and nocturnal denizens of dense primary forest. More recent observations suggest that they may not be as arboreal and nocturnal as previously thought. They may use trees as day time rest sites but also spend a significant proportion of time on the ground. Some daytime movement has been observed suggesting that they are not strictly nocturnal but crepuscular. However, the time of day when they are active depends on their prey and the level of human disturbance.
Their prey likely includes both arboreal and terrestrial vertebrates. Pocock presumed that they are adapted for preying upon herbivorous mammals of considerable bulk because of their powerful build, the deep penetration of their bite, attested by their long canines. Confirmed prey species include hog deer, slow loris, brush-tailed porcupine, Malayan pangolin and Indochinese ground squirrel. Known prey species in China include barking deer and pheasants. They most likely also hunt civets, birds, and domestic livestock. Captive clouded leopards also eat eggs and some vegetation.