TiddlyWiki er en personlig wiki og en ikke-lineær notatbok for organisering og deling av kompleks informasjon. Det er en åpen kildekode for enkeltsideapplikasjonswiki i form av en enkelt HTML-fil som inkluderer CSS, JavaScript og innholdet. Den er designet for å være enkel å tilpasse og omforme avhengig av bruksområde. Det letter gjenbruk av innhold ved å dele det opp i små biter kalt Tiddlers.

TiddlyWiki is designed for customization and to be shaped according to users’ specific needs, perhaps comparable to a high-end programming language. As such, it can be shaped into a wide and arbitrary range of special applications. Examples include niche note taking applications, to-do lists, presentations, collections, authoring tools, personal databases, recipe collections, etc.

Although there are many TiddlyWiki documents on the Web, the majority of TiddlyWikis reside on personal computers or in the cloud, or are exchanged over email, in a manner similar to word processing documents and spreadsheets. As a single HTML file, or saved as an HTA file in Microsoft Windows (allowing corporate IE lockdown to be bypassed), TiddlyWiki can be useful in corporate environments where red tape or IT resources might prevent the use of a wiki that requires a more complicated installation.