Peroxisomes are spherical organels present in almost all eukaryotic cells. They are enclosed in a single membrane, they do not have their own genetic material and their primary function is oxidation of different substrates. Key metabolic roles of peroxisomes are β-oxidation, detoxification of reactive oxygen species, and glyoxylate cycle and photorespiration in plant cells. Peroxisomes arise by division of existing peroxisomes by mechanism like that of mitochondria or by de novo biogenesis by budding of vesicles from endoplasmic reticulum. Peroxins are proteins important for peroxisomal biogenesis. Peroxisomal proteins are synthesized on free ribosomes in cells and are posttranslationally imported in folded or oligomeric shape through transient pore on peroxisomal membrane. Peroxins Pex5 and Pex7 are soluble receptors for matrix protein import and Pex19 is a receptor for import of peroxisomal membrane proteins. Number of peroxisomes in cells is regulated and there are mechanisms that direct inheritance of peroxisomes during cell division. Peroxisomes are mostly degraded by pexophagy which is mostly regulated by ubiquitination. Peroxisome disorders can be caused by a single enzyme deficiency, such as in X-linked adrenoleukodystrophy, or by absence of functional peroxisomes, such as in Zellweger syndrome.