Microalgae have long been recognised for their nutritional value and high protein contents. With the increasing demand for “vegan protein” and concerns for global food security, microalgal protein is finding renewed interest. Microalgae are highly productive and can be grown without competing for arable land or freshwater resources. Most microalgal protein contains all essential amino acids and is hence more suitable as a meat replacement than any other plant protein. Microalgal products are also readily suitable for cosmetic and nutraceutical applications due to their significant health benefits. This chapter provides an overview of the use of various protein-rich microalgae in food, feed, nutraceuticals, and cosmetics. The latest technical advances in protein extraction from microalgae are presented, together with an overview of current knowledge on bioavailability and digestibility of microalgal proteins.