The Random House Dictionary of the English Language, Unabridged was the original name of a large American dictionary, first published in 1966, and recently renamed the Random House Webster's Unabridged Dictionary.

The Random House publishing company entered the reference book market after World War II. Its first dictionary was Clarence Barnhart's American College Dictionary, published in 1947. Random House acquired the rights to the Century Dictionary, its successor the New Century Dictionary, and the Dictionary of American English, all out of print.

Following the mixed reception of Webster's Third New International Dictionary, Unabridged, published in 1961, Random House decided to enter the market with a larger dictionary. Under editors Jess Stein and Lawrence Urdang, they augmented the American College Dictionary with large numbers of proper names, and published it in 1966 as the first edition of the Random House Dictionary of the English Language. Unabridged. It was the first dictionary to use computer typesetting.

An expanded second edition, edited by Stuart Berg Flexner, appeared in 1987, revised in 1993. This edition adopted the Merriam-Webster Collegiate innovation of adding dates for the entry of words into the language. Unlike the Collegiate, which cited the date of the first known citation, Random House indicated a range of dates. For example, where the Collegiate gave 1676, Random House might offer, 1670-80.

Random House incorporated the name Webster's into it's title after an injunction won by Merriam Webster preventing its use on their college edition was overturned on appeal. The name Random House Webster's is now used on many Random House publications.

Versions of the dictionary have been published under other names, including Webster's New Universal Dictionary (which was previously the name of an entirely different dictionary.)