What is the smallest mammal by size?

The smallest mammal by size is the bumblebee bat (Craseonycteris thonglongyai), found in Thailand and Myanmar. Weighing only about 2 grams (0.07 ounces) and measuring around 3 to 4 centimeters (1.2 to 1.6 inches) in length, this tiny bat is about the size of a bumblebee. Despite its small size, the bumblebee bat is a highly skilled insect hunter, using echolocation to navigate and locate prey in the dark.