The classification of tiger subspecies has evolved over time. Initially, several subspecies were described based on physical characteristics. However, a 2015 study and subsequent revisions by the IUCN Cat Specialist Group proposed recognizing only two subspecies:

• Panthera tigris tigris: This subspecies includes the Bengal, Malayan, Indochinese, South Chinese, and Siberian tiger populations in mainland Asia.
• Panthera tigris sondaica: This subspecies includes the Javan, Bali, and Sumatran tiger populations of the Sunda Islands.

These two groups further constitute clades within themselves. This two-subspecies classification is still debated, with genetic analysis supporting the distinction of six monophyletic clades corresponding to the living subspecies: Bengal Tiger (P. t. tigris), Siberian Tiger (P. t. altaica), South China Tiger (P. t. amoyensis), Indochinese Tiger (P. t. corbetti), Malayan Tiger (P. t. jacksoni) and Sumatran Tiger (P. t. sumatrae).

Tigers and snow leopards are connected through a shared evolutionary lineage, having diverged from other Panthera species about 2.88 million years ago. The origin of this lineage can be traced to northern Central Asia, and over time it dispersed into Southeast Asia during the Miocene period. This elaborates their evolutionary ties and their geographical range expansion.

The body weight of male tigers ranges from 100 to 261 kg (200-575 lb), with individuals in captivity reaching up to 325 kg (716 lb). Females typically weigh between 75 and 177 kg (170-390 lb). In terms of head-body length, male tigers measure from 189 to 300 cm (6.20-10 ft), while females range from 146 to 177 cm (4.79-5.81 ft). The shoulder height of these big cats is approximately 80-100 cm (3 ft), and their tail length spans from 72 to 109 cm (2.4-3.58 ft). Tigers exhibit a distinctive pelage characterized by black or brown stripes on a red-orange to golden-yellow background, contributing to their iconic and recognizable appearance.

Globally, the tiger population stands at 5,574 in 2023, experiencing a notable increase. India and Nepal played a significant role in this growth, with both countries effectively doubling their tiger numbers during a period to 2016 to 2023. India is home for more than 70% of world’s wild tiger population.

Over the past century, global tiger numbers have drastically declined. A 2006 habitat study revealed that the remaining tiger population now occupies 40 percent less area than they did just a decade ago, limiting them to only seven percent of their historic range. There are 13 range countries in Asia where tigers are found namely; Bangladesh, Bhutan, Cambodia, China, India, Indonesia, Lao PDR, Malaysia, Myanmar, Nepal, Russia, Thailand and Vietnam. While the wild tiger status is good in South Asia, it is alarming in the South East Asia. Cambodia, Lao-PDR and Vietnam have lost their tigers. The situation is grim in other Tiger Range Countries of the said region.

Tigers exhibit a broad ecological range, populating diverse habitats that span evergreen forests, rainforests, temperate forests, deciduous forests, grasslands, and mangrove swamps. Their adaptability extends to tropical deciduous, semi-evergreen, and evergreen forests, as well as montane forests, peat swamps, and the remaining blocks of lowland rainforest. This versatility in habitat preferences underscores the tiger's ability to thrive across various landscapes, showcasing their adaptability to a wide array of environmental conditions.

Tigers reach sexual maturity at different ages, with males typically achieving it between 4 to 5 years, and females at 3 to 4 years.
Average gestation period: 103 to 106 days
Average Litter size: 2 to 3 cubs
Average life expectancy: 12 to 16 years (both in wild and captivity)

Tigers exhibit varying activity patterns, being active both day and night unless they face human threats. Their social behavior is predominantly solitary, with the exception of females nurturing cubs and temporary associations during mating. Females maintain smaller, distinct territories while males encompass ranges that include multiple (3-5) female territories without overlapping with other males. They typically hunt alone, relying on a stalk-and-ambush strategy to capture prey, often killing by biting the back of the neck or using throat bites for strangulation. Tigers communicate through a variety of vocalizations. Scent-marking is a common behavior across their territorial range, complemented by visual signals involving posture and facial expressions to convey intentions, particularly in close interactions.

Tigers, being the largest carnivore species on land in their regions, primarily consume large and medium-sized deer, wild pigs, antelope, water buffalo, and sometime domestic livestock. They exhibit a preference for large ungulates, making them the mainstay of their diet across diverse ecosystems, constituting nearly 75% of a tiger's diet by mass. Tigers display opportunistic behavior, occasionally consuming a variety of other animals, including primates, birds, reptiles, amphibians, fish, and even invertebrates. Tigers tend to target larger prey more frequently than smaller prey, with an average prey size of 97 kg (214 lb) for tigers, in contrast to 28 kg (62 lb) for leopards.

IUCN has listed tigers as Endangered in 2021 although sub-species level listing is under review. The tiger is protected over most of its range and commercial trade is long prohibited.

Major threats include:

• Habitat loss and fragmentation
• Illegal demand of illegal body parts
• Loss of wild prey
• Conflict with humans
• Shared resources with humans