ShapeWriter (previously known as Shorthand-Aided Rapid Keyboarding (SHARK)) was a keyboard text input method for tablet, handheld PCs, and mobile phones invented by Shumin Zhai and Per Ola Kristensson at IBM Almaden Research Center and the Department of Computer and Information Science at Linköping University.

Using ShapeWriter text entry software, a user draws words on a graphical keyboard using a pen. Instead of tapping the keys, the user draws a pen gesture that connects all the letters in the desired word. After some usage the user learns the movement pattern for the commonly used words and can write them faster than is possible on a traditional virtual keyboard.

The first system described by Shumin Zhai and Per Ola Kristensson (2003) was only a prototype system that could recognize about 100 pen gestures for the top 100 words used in the English language. It used a handwriting recognition algorithm that relied on dynamic programming to recognize the word patterns drawn from a lexicon. The next version described by Per Ola Kristensson and Shumin Zhai (2004) has a fundamentally different recognition engine that can recognize 50,000 - 60,000 words with low latency. This system introduced the notion that every word in a large lexicon should be possible to write by tracing the letters. It is this system that was the basis for the software release on IBM alphaWorks that is generally associated with the term "ShapeWriter".

ShapeWriter was acquired by Nuance Communications, and taken off the market in 2010; its technology presumably incorporated as part of Nuance's FlexT9 app in 2011.