A Rolodex is a rotating card file device used to store a contact list. Its name, a portmanteau of the words "rolling" and "index", has become somewhat genericized for any personal organizer performing this function, or as a metonym for a total accumulation of business contacts. In this usage, it has generally come to describe an effect or characteristic of the small-world network of a business's investors, board of directors, or the value of a CEO's contacts, or in organizational structure. Models have been exhibited in the Smithsonian Institution.
The Rolodex was invented in 1956 by Danish engineer Hildaur Neilsen, the chief engineer of Arnold Neustadter's company Zephyr American, a stationery manufacturer in New York. Neustadter was often credited with having invented it. First marketed in 1958, it was an improvement to an earlier design called the Wheeldex. Zephyr American also invented, manufactured and sold the Autodex, a spring-operated phone directory that automatically opened to the selected letter; Swivodex, an inkwell that did not spill; Punchodex, a paper hole puncher; and Clipodex, an office aid that attached to a stenographer's knee.
Rolodex also marketed non-rotary (linear) tub-like card-file systems using the same cards (size and notches) as the rotary files.
Neustadter retired and sold out to a larger firm in 1970. As of 2023, Rolodex card files are still made.
File:RolodexTM 67236 Rotary Business Card File.jpg|right|Rolodex 67236 rotary business card file
File:Rolodex with Altered Cards.jpg|A decorative rolodex
File:Decorative Rolodex 2.jpg|A decorative rolodex
File:Rolodex Cards - End of Box.jpg|Rolodex cards refill box
File:A large filled rolodex viewed from the side.jpg|A large filled rolodex viewed from the side
File:Rolodex-Linear.