Are dolphins whales?

The Relationship Between Dolphins and Whales

The question of whether dolphins are whales depends on how you define “whale.” In everyday language, people use “whale” to describe large cetaceans and “dolphin” for smaller ones. But in scientific classification, dolphins are a subset of whales — specifically, they are toothed whales belonging to the suborder Odontoceti.

Understanding Cetacean Classification

All cetaceans — whales, dolphins, and porpoises — belong to the order Cetacea. This order is divided into two living suborders:

Mysticeti (Baleen Whales)

• Have baleen plates instead of teeth
• Generally larger body size
• Includes blue whales, humpback whales, gray whales, and right whales

Odontoceti (Toothed Whales)

• Have teeth
• Use echolocation
• Includes sperm whales, beaked whales, dolphins, and porpoises

Since dolphins fall within Odontoceti — the toothed whale suborder — they are, by definition, whales in the taxonomic sense.

The Dolphin Family

Most of what people call “dolphins” belong to the family Delphinidae (oceanic dolphins), which contains approximately 36 species. This family includes:

• Bottlenose dolphins
• Common dolphins
• Spinner dolphins
• Pilot whales (which are actually dolphins despite the name)
• Orcas/killer whales (the largest dolphin species)

There are also river dolphin families (Iniidae, Platanistidae, Pontoporiidae) that are more distantly related to oceanic dolphins.

Why the Confusion Exists

The confusion arises because the common English word “whale” does not correspond to a single scientific group. Instead, “whale” is an informal term that has historically been applied to the larger cetaceans. Several members of the dolphin family carry the common name “whale” precisely because of their large size:

• Killer whales (orcas) — actually the largest dolphins
• Pilot whales — actually large dolphins
• Melon-headed whales — actually dolphins
• False killer whales — actually dolphins

Meanwhile, sperm whales are called “whales” and are toothed whales, but they are not dolphins. They belong to a separate family (Physeteridae) within the same suborder.

Dolphins vs. Porpoises

People also frequently confuse dolphins with porpoises. While both are toothed whales (Odontoceti), they belong to different families:

Feature	Dolphins (Delphinidae)	Porpoises (Phocoenidae)
Teeth	Cone-shaped	Spade-shaped (flat)
Snout	Elongated beak	Short, blunt
Body size	Varies widely	Generally smaller
Dorsal fin	Curved/hooked	Triangular
Social behavior	Large groups	Smaller groups
Species count	~36 species	~7 species

The Simple Answer

Think of it as a set of nested categories:

1. Cetaceans = all whales, dolphins, and porpoises
2. Whales (informal) = the larger cetaceans
3. Toothed whales (Odontoceti) = includes dolphins, porpoises, sperm whales, and beaked whales
4. Dolphins (Delphinidae) = a specific family within the toothed whales

So yes, dolphins are whales — but they are a specific type of whale. For the related question about orcas specifically, see are orcas whales and are killer whales dolphins.