Macroautophagy is an intracellular degradation system that delivers diverse cytoplasmic materials to lysosomes via autophagosomes. Recent advances have enabled identification of several selective autophagy substrates and receptors, greatly expanding our understanding of the cellular functions of autophagy. In this review, we describe the diverse cellular functions of macroautophagy, including its essential contribution to metabolic adaptation and cellular homeostasis. We also discuss emerging findings on the mechanisms and functions of various types of selective autophagy. Expected final online publication date for the Annual Review of Cell and Developmental Biology Volume 35 is October 7, 2019. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.