Which breed has the highest average weight of any dog breed?

The English Mastiff has the highest average weight of any dog breed.

Often called simply the Mastiff, this British breed is built for mass rather than height. Its exceptionally broad chest, heavy bone, deep body, and large head give it more average body weight than other familiar giant breeds. The English Mastiff is generally regarded as the largest living dog breed by mass.

That distinction is easy to confuse with height. Great Danes and Irish Wolfhounds are usually taller, but their lighter frames mean they do not match the Mastiff’s average bulk. Saint Bernards can overlap substantially in weight, and individual dogs from several giant breeds may be heavier than an individual Mastiff.

The breed’s size also explains famous historical records. An English Mastiff named Aicama Zorba of La Susa was recorded at 343 pounds (155.6 kilograms), though exceptional individual records should not be mistaken for a breed average. Modern breed descriptions often give broad male and female ranges rather than a single ideal weight, since healthy size varies by sex, lineage, and body condition. “Largest by weight” is therefore the key distinction in this question.