SMS language or textese (also known as txt-speak, txtese, chatspeak, txt, txtspk, txtk, txto, texting language, txt lingo, SMSish, txtslang,or txt talk) is a term for the abbreviations and slang most commonly used due to the necessary brevity of mobile phone text messaging, in particular the widespread SMS (Short Message Service) communication protocol. Some similarities and overlaps in properties and style can be found within SMS language and Internet-based communication such as email and instant messaging.

SMS language is similar to that used by those sending telegraphs that charged by the word. It seeks to use the fewest number of letters to produce ultra-concise words and sentiments in dealing with space, time and cost constraints of text messaging. This is following how early SMS permitted only 160 characters and some carriers charge messages by the number of characters sent .

It also shares some of these characteristics with Internet slang and Telex speak following how its evolution is rather symbiotic to the evolution of use of shorthand in Internet chat rooms. Likewise, such an evolution sought to accommodate the small number of characters allowed per message, and as a convenient language for the time-consuming and at times, small keyboards on mobile phones. In addition, similarly elliptical styles of writing can be traced to the days of telegraphese 120 years back, where telegraph operators were reported to use abbreviations similar to those used in modern text when chatting amongst themselves in between sending of official messages.