The biggest dog breed depends on whether you mean heaviest or tallest. By weight it's the English Mastiff — the heaviest dogs ever recorded have been Mastiffs. By height it's the Irish Wolfhound as a breed average, though the tallest individual dogs on record have been Great Danes.
Here's how the giants compare, and what living with one actually involves.
The heaviest dog breeds
| Breed | Typical weight | Typical height (shoulder) |
|---|---|---|
| English Mastiff | 120–230 lb | 27–33 in |
| Saint Bernard | 120–180 lb | 26–30 in |
| Tibetan Mastiff | 90–160 lb | 24–30 in |
| Neapolitan Mastiff | 110–150 lb | 24–31 in |
| Newfoundland | 100–150 lb | 26–28 in |
| Leonberger | 90–170 lb | 25–31 in |
| Kangal | 90–145 lb | 28–32 in |
| Anatolian Shepherd | 80–150 lb | 27–29 in |
The English Mastiff wins on sheer mass. It's a broad, heavy-boned breed, and the record-holding individuals have been extraordinary outliers rather than anything to expect from a pet.
The tallest dog breeds
| Breed | Typical height (shoulder) | Typical weight |
|---|---|---|
| Irish Wolfhound | 30–35 in | 105–180 lb |
| Great Dane | 28–34 in | 110–175 lb |
| Scottish Deerhound | 28–32 in | 75–110 lb |
| Borzoi | 26–32 in | 60–105 lb |
The Irish Wolfhound is the tallest breed on average — it's the breed standard's minimum heights that put it ahead. Great Danes are heavier for their height and have produced the tallest individual dogs ever measured, standing well over three feet at the shoulder.
Standing on their hind legs, both routinely reach the height of an adult human, which is worth knowing before you leave food on a counter.
What owning a giant breed actually involves
They don't live as long
This is the hardest part. Giant breeds generally have shorter lifespans than small dogs — many average six to ten years, and some of the largest sit at the lower end of that. Size and longevity trade off against each other in dogs.
Health risks scale with size
- Hip and elbow dysplasia — ask any breeder for joint scores on both parents
- Bloat (gastric dilatation-volvulus) — a true emergency, and deep-chested giants are the highest-risk group. Learn the signs: unproductive retching, a distended abdomen, restlessness and distress. It needs a vet within the hour.
- Dilated cardiomyopathy, particularly in Great Danes and Dobermans
- Osteosarcoma — bone cancer is more common in large breeds
- Joint strain, worsened by any excess weight
Puppies grow slowly and need managing
Giant-breed puppies need large-breed puppy food with controlled calcium and energy density, because growing too fast damages developing joints. They also shouldn't do repetitive high-impact exercise — long runs, jumping, stairs — until their growth plates close, which can take 18 months or more.
Everything costs more
Food, medication dosed by weight, boarding, insurance, a car that fits them, and a vet bill that scales with body mass. Anaesthesia and surgery on a 150 lb dog is not the same undertaking as on a 15 lb one.
Are giant breeds good family dogs?
Many are famously gentle — Newfoundlands, Saint Bernards and Great Danes all have strong reputations with children. But size makes calmness non-negotiable: a friendly 150 lb dog who jumps up can knock over a child or an older adult without any intent to. Early training and consistent manners matter more for giants than for any other group, because the same behaviour has bigger consequences.
Guardian breeds like the Kangal, Anatolian Shepherd and Tibetan Mastiff are a different proposition. They were bred to make independent decisions about threats, and they need experienced owners rather than simply willing ones.
The short answer
The English Mastiff is the heaviest dog breed, and the Irish Wolfhound is the tallest by breed average, with Great Danes producing the tallest individuals on record. All of the giants share the same trade-off: remarkable dogs, shorter lives, higher health risks and real cost. Worth going in with eyes open.