This is a well-known whale, with a stout body and very long flippers that have bumps and lumps upon which barnacles may grow. The head is rounded and flat, apart from the raised lumps ('tubercles') which are also found on the lower jaw. The dorsal fin is varied in size and shape from individual to individual, and tail flukes are large and almost 'wing-shaped'.

The Humpback Whale is black to blue-black in color, with pale to white undersides that can show black markings that are varied according to individual. It is with these markings that individual whales can be identified. They measure between 12-14m in length, with the females generally larger than the males, and they weigh between 25-30 tons. There are 12-36 throat grooves and between 540-800 baleen plates per animal, the longest reaching between 80-100cm.

This is a species that it unmistakable at sea, through the combination of the big, sometimes bushy blow, dark skin color, the shape of the dorsal, and its habit of raising the flukes on diving. Lob tailing, flipper-slapping and breaching (these whales are very acrobatic) are also other giveaways. As Mark Carwardine said in On the Trail of The Whale, "look for a giant black Cadillac with a radiator problem".

The Humpback Whale is found from the topics to the polar waters, and spends a lot of time in much shallower, offshore waters than other rorquals. However, they also cross thousands of kilometers of open ocean when migrating between summer and winter grounds.
Humpback Whales tend to feed within 50m of the water's surface, taking krill and shoaling fish such as herring, sand eel, capelin, and mackerel. This is another 'gulping' whale, filtering food from masses of tons of water through the baleen plates after engulfing a mouthful. Unlike other rorquals, the Humpback has many varied methods of feeding, including lunge-feeding, tail-flicking and bubble-netting, the latter of which is a favorite subject for nature documentaries.

When lunge-feeding, the whale swims through a shoal of its prey with its mouth open, often exploding at the surface with both food and water pouring from the mouth's sides. When tail-flicking, the whale lies in a belly-up position just below the surface with its mouth open, and then flicks its tail clear of the water, casting the prey up into the air and down into its mouth. Bubble-netting, though, is by far the most outstanding. The whale dives beneath a shoal of prey and slowly begins to spiral upwards, blowing bubbles in a circular shape (and emitting a steam-engine sound) as it does so. These bubbles tend to congregate the prey in the center of the circle, and the ones blown at the bottom of the spiral reach the surface at the same time as the ones blown last. Then the whale returns to beneath the prey and swims up through the bubble-net into the center with its mouth open to gulp up all the prey, as shown.

Humpback Whales often congregate in large, loose groups of tens of animals for breeding and feeding, but within these groups they move individually or in the companionship of between 1-3 others. On breeding grounds the well-known 'gentleness' of these animals is abandoned, with males becoming very aggressive as they attempt to claim females for their own. It is with these breeding grounds that the Humpbacks are most commonly associated with their 'singing', which is well-known for being included on the Voyager space mission, along with the gulden plaque. The songs can vary from 35 minutes to days in length, with pauses only for breath. It is the males that sing in this fashion. The most acrobatic of large whales, Humpbacks are also well-known for their breaches - one was recorded breaching 200 times in a row - lob-tailing and flipper-slapping. Some Humpbacks in Alaska have been seen ruling over icebergs in play.