In their native South Africa, these powerful farm dogs fend off fierce predators like leopards. Because of their strength and dominance, the AKC recommends prior experience owning large breeds before adopting a Boerboel.

• Weight: 150 to 200 pounds
• Height: 22 to 27 inches
  

According to the AKC, Tosa dogs (Japanese Mastiff) used to be bred for fighting but are now used as watchdogs, a position perfect for their calm, patient and vigilant personalities.

• Weight: 100 to 200 pounds
• Height: 21.5 to 23.5 inches
  

Known as the friendly giant of the Swiss Alps, according to the AKC, Saint Bernards are gentle and tolerant, especially with children. They don't fawn over strangers and can be used as a watchdog.

• Weight: 120 to 180 pounds
• Height: 26 to 30 inches
  

Gentle and loving, this breed is excellent for kids. According to the AKC, Great Danes are alert guards, but not overly aggressive. They're moderately intelligent, but highly stubborn and not easily trained.

• Weight: 110 to 175 pounds
• Height: 28 to 32 inches

Affectionate might be an understatement — Leos want to be with their families at all times! DogTime states the breed is a mix of some of the other largest dogs— the Newfoundland, Saint Bernard and Great Pyrenees. These sweet companions have the potential to be excellent therapy dogs, but probably not lapdogs.

• Weight: 90 to 170 pounds
• Height: 25.5 to 31.5 inches
  

With a droopy face and a tendency to drool, Mastinos may look a little dopey (just think of Hagrid's dog Fang in the Harry Potter movies), but they're really designed to be protective guard dogs. Not for novice pet owners, this 150-pound canine is both massive and powerful.

• Weight: 110 to 150 pounds
• Height: 24 to 31 inches
  

This lovable dog was the model for the nursemaid dog in Peter Pan. According to DogTime, Newfoundlands love children of all ages and are intelligent, with a strong desire to please.

• Weight: 100 to 150 pounds
• Height: 26 to 28 inches

Despite the misleading name, Anatolians are bred as guard dogs, not herders. They can be protective and territorial, but still calm and affectionate with their families, according to PetMD.

• Weight: 80 to 150 pounds
• Height: 27 to 29 inches
  

Brave, affectionate, and loyal, Bullmastiff dogs can be both great family members and protectors. They're especially willing to please and, despite their large stature, don't require much exercise.

• Weight: 100 to 130 pounds
• Height: 24 to 27 inches
  

Alpine farmers bred Greater Swiss Mountain Dogs for their versatility, combining strength and agility for a true workhorse. Families can appreciate their even-tempered nature — and the undeniably sweet expressions.

• Weight: 85 to 140 pounds
• Height: 23.7 to 28.5 inches
  

Potential adopters, be warned: TMs are notorious for not coming when called, plus they have a (destructive) fondness for wood, according to the AKC. That said, the fluffy guard dogs are intelligent and devoted, not to mention seriously adorable.

• Weight: 70 to 150 pounds
• Height: 24 to 26 inches
  

Dignified and slow to anger, Rottweilers are trustworthy around children if raised with them, the AKC states. Their natural guarding instinct is coupled with great courage. They're obedient and moderately intelligent.

• Weight: 80 to 135 pounds
• Height: 22 to 27 inches
  

Not all terriers stay small. These massive guard dogs can back up their bark with a 130-pound frame, as they're protective of their owners and suspicious of strangers. Given those thick double coats, a home in a cold climate is a plus.

• Weight: 80 to 130 pounds
• Height: 26 to 30 inches

Believed to be the oldest dog breed in Portugal, the Estrela Mountain Dog is an excellent companion and livestock guardian, according to the AKC. No thief is safe around these dogs– they aren’t afraid to protect their owners against any distrustful strangers.

• Weight: 77 to 132 pounds
• Height: 24.5 to 29 inches
  

You'll recognize this lovable sidekick from the Tom Hanks movie Turner and Hooch, but off the silver screen, these French mastiffs are just as eager to please. The Dogue de Bordeaux is courageous and loyal but not aggressive.

• Weight: 99 to 110 pounds
• Height: 23 to 26 inches
  

As the tallest breed, Irish Wolfhounds may look imposing, but they're really the definition of a gentle giant. These sweet-hearted pets get along wonderfully with kids.

• Weight: 105 to 120 pounds
• Height: 30 to 32 inches
  

These strong-willed, instinctual, and dominant hunting dogs are not for first-time owners. DogTime states they're naturally protective and defensive of their families. But they're can be suitable for well-behaved children if raised with them (and supervised by adults).

• Weight: 70 to 130 pounds
• Height: 24 to 28 inches
  

Cane Corsi, also called Italian Mastiffs, can be intimidating bodyguards that need lots of exercise and a firm hand. With the right training; however, these fierce canines will bond with their families, including children.

• Weight: 80 to 120 pounds
• Height: 23.5 to 27.5 inches

Ideally suited for otter hunting, a now out-lawed activity in England, Otterhound dogs are known for their strong sense of smell, swimming ability and powerful chest and shoulders, according to DogTime. These dogs bred in the UK can weigh up to 115 pounds and stand over two feet tall.

• Weight: 80 to 115 pounds
• Height: 24 to 27 inches