Xmas is a common abbreviation of the word Christmas . It is sometimes pronounced /krim/, but it, and variants such as Xtemass, originated as handwriting abbreviations for the typical pronunciation /krɪsməs/. The "-mas" part is from the Latin-derived Old English word for Mass, while the "X" comes from the Greek letter Chi, which is the first letter of the Greek word Xpiσtó which comes into English as "Christ."

There is a common misconception that the word Xmas stems from a secular attempt to remove the religious tradition from Christmas by taking the "Christ" out of "Christmas," but its use dates back to the 16th century.

Early use of "Xmas" includes Bernard Ward's History of St. Edmund's college, Old Hall (originally published circa 1755). An earlier version, "X'temmas", dates to 1551. Around 1100 the term was written as "Xpes mæsse" in the Anglo-Saxon Chronicle. "Xmas" is found in a letter from George Woodward in 1753. Lord Byron used the term in 1811, as did Samuel Coleridge (1801)and Lewis Carroll (1864). In the United States, Oliver Wendell Holmes, Jr. used the term in a letter dated 1923. Since at least the late 19th century, "Xmas" has been in use in various other English-language nations. Quotations with the word can be found in texts first written in Canada, and the word has been used in Australia, and in the Caribbean. Merriam-Webster's Dictionary of English Usage stated that modern use of the term is largely limited to advertisements, headlines and banners, where its conciseness is valued. The association with commerce "has done nothing for its reputation," according to the dictionary.

In the United Kingdom, the former Church of England Bishop of Blackburn, Alan Chesters, recommended to his clergy that they avoid the spelling. In the United States, in 1977 New Hampshire Governor Meldrim Thomson sent out a press release saying that he wanted journalists to keep the "Christ" in Christmas, and not call it Xmas - which he asserted was a "pagan" spelling of Christmas.

This usage of "X" to spell the syllable "kris" (rather than the sounds "ks") has extended to "xtal" for "crystal", and on florists' signs to "xant" for "chrysanthemum," even though these words are not etymologically related to "Christ": "crystal" comes from a Greek word meaning "ice" (and not even using the letter X), and "chrysanthemum" comes from Greek words meaning "golden flower," while "Christ" comes from a Greek word meaning "anointed."