Nickel in elemental form or alloyed with other metals and materials has made significant contributions to our present-day society and promises to continue to supply materials for a demanding future. This Article provides a historical overview and physical metallurgy of nickel and nickel alloys. It lists and describes the compositions, mechanical and physical properties, and applications of commercial nickel and its alloys. The Article briefly explains the forms of corrosion resulting from the exposure of nickel alloys to aqueous environments. It provides valuable information on the commercial forms of nickel alloys, namely, nickel-copper alloys, nickel-chromium and nickel-chromium-iron series, iron-nickel-chromium alloys, controlled-expansion alloys, nickel-iron low-expansion alloys, soft magnetic alloys, and welding alloys.