With so many breeds to choose from, there truly is something for everyone in this mid-size category. They may be defined by their weight but certainly not by their personalities. That’s probably why several of these dogs show up on the most popular dog lists year after year. Many have been around for hundreds of years, and some, quite literally, thousands of years. They guard livestock, pull sleds, and hunt everything from lions and bears to birds. On the other hand, many mid-sized dogs have sweet and calm demeanors, making them excellent support animals for those with disabilities or simply cuddly companions for those looking for an oversized lap dog. Since individual weights can vary from dog to dog, don’t be surprised if your medium-sized breed doesn’t fit neatly in the 21 to 50 lb range. It’s normal for some to be slightly lighter or heavier. Select from the popular breeds above to learn more, or use our Breed Explorer to find any medium dog breed you're looking for.