In addition to the established magnetic mass storage media (floppy disk, hard disk, tape) optical mass storage media (CD‐ROM (compact disk‐read only memory), WORM (write once, read many times), EOD (erasable optical disk)) are increasingly used. Generally, magnetic and optical media do not compete, but complement each other due to their specific advantages. Progress in optical data storage technology is closely connected with the development of suitable materials. This article illustrates in detail the current state of the art and the ongoing development of materials for optical data storage. For the information layer of WORM disks, dyes with high ir absorption, low heat conductivity, and good solubility are required. Besides polymethine dyes, biaxially substituted silicon–naphthalocyanines are used; also combinations of metal complexes are employed. The magneto‐optical materials for EOD‐disks in MOR (magneto‐optical recording) technique are primarily ferrimagnetic ternary amorphous alloys of rare‐earth (RE) and transition‐metals (TM) (GdTbFe, TbFeCo, DyFeCo). Ferrites with spinel‐ or garnet‐structure, eg, rare‐earth iron‐garnets (RIG), are commercially unimportant mainly due to their high deposition temperature. Co/Pt‐multilayers (MLs) exhibit interesting properties, but are still waiting for commercial introduction. Research concentrates on exchange‐coupled RE‐TM layers, which permit a direct overwrite procedure. Phase‐change materials for EOD‐disks in PCR (phase‐change recording) technique are primarily ternary alloys (eg, GeSbTe, InSbTe). Research focuses on materials with fast crystallization in parallel with high stability even at numerous write/read/erase cycles. As substrate materials for CD‐ROM disks, end group‐modified bisphenol A–polycarbonate (BPA‐PC) is employed exclusively. For WORM and EOD disks mainly BPA‐PC and sometimes glass is applied.