Smallest mammal (by mass)

The world's smallest mammal by mass is the Etruscan shrew (Suncus etruscus), of the Mediterranean and southern Asia regions. Adults weigh on average 1.8 g (0.063 oz), with a range of 1.5–2.6 g (0.05–0.09 oz) and measure about the size of a thumb, with an average body length of 36–53 mm (1.4–2 in), with a 24–29-mm-long (0.9–1-in) tail.

By body length, the Etruscan shrew is superseded by the Kitti's hog-nosed bat (Craseonycteris thonglongyai), with a body no bigger than a large bumblebee (hence why it is often called the bumblebee bat). It has a head-body length of only 29–33 mm (1.14–1.29 in), a wingspan of approximately 130–145 mm (5.1–5.7 in), and a weight of around 2 g (0.07 oz). The tiny bat can be found only in a few select limestone caves on the Khwae Noi River in Kanchanaburi Province, western Thailand and in south-east Myanmar.