The True Titans: Meet Reginald "Reggie" Reiss, The World's Tallest Living Dog (Updated December 2025)

The title of the "biggest dog in the world" is not held by a single champion, but is split across multiple, awe-inspiring records. As of December 2025, the official Guinness World Record holder for the Tallest Living Dog is Reginald "Reggie" Johnson Reiss, a magnificent Great Dane whose height at the withers rivals that of a small pony. The world of giant breeds is constantly changing, with previous record holders like Kevin and another Great Dane named Zeus having recently held the coveted title, but a new titan has stepped forward to claim the crown, demanding special attention and care from his owners.

This article dives deep into the monumental canines that hold the world records for height and weight, providing the most current information available in late 2025. We will explore the latest titleholder, the all-time legends, and most importantly, the specialized care required for these gentle giants, whose enormous size makes them prone to specific, serious health issues.

Meet the Record Holders: Tallest and Heaviest Dogs in History

The term "biggest dog" is typically measured in two distinct categories: height (from foot to withers, or the shoulder blade) and weight. The current and all-time champions represent the pinnacle of their respective breeds, the Great Dane and the English Mastiff.

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Current Tallest Living Dog: Reginald "Reggie" Johnson Reiss

• Name: Reginald “Reggie” Johnson Reiss
• Breed: Great Dane
• Record Verified: January 27, 2025
• Height: 1.007 meters (3 feet 3 inches) to the withers
• Location: Idaho Falls, Idaho, USA
• Fun Fact: Reggie is a 7-year-old Great Dane who took the title after the passing of the previous record-holder, Kevin, a Great Dane from Iowa.

Reggie, a gentle giant, stands taller than most three-year-old children. His height of 1.007 meters (3 ft 3 in) is a testament to the Great Dane breed's propensity for towering stature. While he is the tallest *living* dog, his height is still a few inches shy of the all-time record holder.

Tallest Dog Ever: Zeus (The Original)

The record for the tallest dog ever remains unbroken since 2011, held by another Great Dane named Zeus.

• Name: Zeus
• Breed: Great Dane
• Record Verified: October 4, 2011
• Height: 1.118 meters (44 inches or 3 feet 8 inches) to the withers
• Location: Otsego, Michigan, USA
• Note: This Zeus passed away in 2014, but his record stands as the highest measure ever recorded by Guinness World Records.

Heaviest Dog Ever: Aicama Zorba of La-Susa

When it comes to sheer mass and weight, the English Mastiff breed dominates. The all-time heaviest dog was a behemoth named Zorba.

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• Name: Aicama Zorba of La-Susa (Zorba)
• Breed: English Mastiff
• Record Weight: 343 pounds (155.6 kg)
• Length: 8 feet 3 inches (2.51 meters) from nose to tail
• Note: Zorba was a true titan, and while his record dates back to the late 1980s, no dog has officially surpassed his incredible weight and length since.

The Biggest Breeds: A Comparative Look at Giant Canines

The Great Dane and the English Mastiff are not the only contenders for the title of "biggest dog." Several other giant breeds are renowned for their intimidating size, earning them the classification of "Molosser" or "Giant Breed" dogs. These breeds often exceed 100 pounds and require specialized handling and care.

The English Mastiff is often cited as the heaviest breed, with males routinely weighing over 200 pounds. The Great Dane, while often the tallest, is generally lighter. The Irish Wolfhound is a worthy contender for height, frequently being the tallest breed on average, with some individuals reaching up to 3 feet in height at the shoulder.

Other notable giant breeds include the Saint Bernard, Newfoundland, Leonberger, Anatolian Shepherd, Bullmastiff, Dogue de Bordeaux, and the Great Pyrenees. Each of these breeds possesses a loving, gentle temperament that often contrasts with their massive physical appearance.

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Critical Care for Gentle Giants: Health Risks and Lifespan

The immense size of these record-holding dogs and other giant breeds comes with a significant trade-off: a shorter lifespan and a predisposition to severe health conditions. Owners of Great Danes, English Mastiffs, and similar large canines must be vigilant about preventative care to ensure their pets live the longest, healthiest lives possible. The average lifespan for a Great Dane is typically 7 to 10 years, while English Mastiffs often live only 6 to 10 years.

The Threat of Gastric Dilatation-Volvulus (GDV) or Bloat

The most critical and life-threatening health issue for Great Danes and other deep-chested giant breeds is Gastric Dilatation-Volvulus (GDV), commonly known as bloat. This condition occurs when the dog's stomach fills with gas (dilatation) and then twists (volvulus), cutting off blood flow and preventing gas from escaping.

Bloat is a medical emergency that can be fatal within hours. Symptoms include a distended abdomen, unproductive retching, excessive drooling, and restlessness. To mitigate this risk, owners often employ preventative strategies such as:

• Feeding multiple small meals per day instead of one large one.
• Restricting vigorous exercise for one hour before and after meals.
• Using a slow-feeder bowl to prevent rapid eating.
• Considering a prophylactic gastropexy surgery, which tacks the stomach to the abdominal wall to prevent twisting.

Skeletal and Joint Issues in Large Dogs

The rapid growth rate and immense body weight of giant breeds put enormous stress on their joints and skeletal structure. This makes them highly susceptible to conditions like Hip Dysplasia and Elbow Dysplasia, which involve the malformation of the joints.

Furthermore, conditions such as Osteoarthritis are common as the dogs age. Proper nutrition, especially during puppyhood, is vital. Giant breed puppies require a special diet formulated to slow their growth rate, preventing bone and joint problems that occur when they grow too quickly.

Obesity and Cardiac Concerns

While a 343-pound dog like Zorba was an anomaly, maintaining a healthy weight is paramount for all giant breeds. Obesity puts further strain on already compromised joints and can exacerbate heart conditions, which are also common in these large animals. Dilated Cardiomyopathy (DCM), a disease of the heart muscle, is a significant concern for Great Danes.

Regular veterinary check-ups, controlled feeding, and moderate, consistent exercise are essential parts of a giant breed's care regimen. Owning a dog the size of Reginald "Reggie" Reiss or one of the massive English Mastiffs is a rewarding commitment, but it requires a deep understanding of their unique needs to ensure their comfort and longevity.