One of the best known is the Galápagos tortoise, which lives on seven of the islands. It has an average lifespan of more than 150 years.

Within the archipelago, up to 15 subspecies of Galapagos tortoises have been identified, although only 11 survive to this day. Six are found on separate islands; five of them on the volcanoes of Isabela. Several of the surviving subspecies are seriously endangered. One of the subspecies, abingdonii from Pinta Island, is considered extinct. The last known specimen, named Lonesome George, died in captivity on 24 June 2012; George had been mated with female tortoises of several other subspecies, but none of the eggs from these pairings hatched.

The Marine Iguana is also extremely unusual, since it is the only iguana adapted to life in the water. Land iguanas, lava lizards, geckos and other harmless snakes can also be found in the Islands.

The Galapagos land iguana (Conolophus subcristatus) is a species of lizard in the family Iguanidae. It is one of three species of the genus Conolophus. It is endemic to the Galápagos Islands, primarily the islands of Fernandina, Isabela, Santa Cruz, North Seymour, Baltra, and South Plaza.

Beginning in the early 1990s the Galapagos land iguana has been the subject of an active reintroduction campaign on Baltra Island. These animals became extinct on Baltra by 1954, allegedly wiped out by soldiers stationed there who shot the iguanas for amusement. However, in the early 1930s, William Randolph Hearst had translocated a population of land iguanas from Baltra to North Seymour Island, a smaller island just a few hundred metres north of Baltra because he could not understand why no iguanas were present there. Hearst's translocated iguanas survived, and became the breeding stock for the Charles Darwin Research Station captive breeding program which has successfully reintroduced the species to Baltra and a number of other areas. Visitors today frequently see iguanas on both the runway of the Baltra airport or while they cross the road.

The large number and range of birds is also of interest to scientists and tourists. Around 56 varieties live in the archipelago, of which 27 are found only in the Galápagos. Some of these are found only on one island.

The most outstanding are penguins, which live on the colder coasts, Darwin's finches, frigatebirds, albatrosses, gulls, boobies,pelicans and Galápagos Hawks, among others. The Flightless Cormorant, a peculiar bird which has lost the ability to fly, is also part of this rich fauna.

Galápagos fur seals are the smallest of otariids. They have a grayish brown fur coat. The adult males of the species average 1.5 m (4 ft 11 in) in length and 64 kg (141 lb) in mass. The females average 1.2 m (3 ft 11 in) in length and 28 kg (62 lb) in mass. They spend more time out of the water than almost any other seal. On average, 70% of their time is spent on land. Most seal species spend 50% of their time on land and 50% in the water.

On the other hand, there are few mammal species, mostly sea mammals such as whales, dolphins and sea lions. A few species of endemic Galapagos mice (or Rice rats) - the Santiago Galapagos Mouse and the Fernandina Galapagos Mouse - have been recently rediscovered.

On the larger Galápagos Islands, four ecological zones nave been defined: coastal, low or dry, transitional and humid. In the first, species such as myrtle, mangrove and saltbush can be found. In the second grow cactus, the incensé tree, carob tree, poison apple tree, chala and yellow cordia, among others. In the transitional zone taller trees, epiphytes and perennial herbs can be seen. The best known varieties are the cat's claw, espuela de gallo. In the humid sector are the cogojo, Galápagos guava, cat's claw, Galapagos coffee, passionflower and some types of moss, ferns and fungus.