Calibri is a humanist sans-serif typeface family, best known as the new default typeface for the Microsoft Office 2007 suite of applications. It replaces the previous defaults Times New Roman (for Microsoft Word) and Arial (for PowerPoint, Excel and Outlook).

Calibri is one of six new western (Latin, Greek and Cyrillic) ClearType Collection typefaces that come with Microsoft Windows Vista, and is the first sans-serif type to be designated the default face for the word-processing application Microsoft Word. Earlier releases of Microsoft Word have consistently used Times New Roman as the default typeface.

Calibri was designed by Lucas de Groot for Microsoft to take advantage of Microsoft's ClearType rendering technology. The typeface won an award in the Type System category at the Type Directors Club's Type Design Competition in 2005. It includes characters from Latin, Latin extended, Greek, and Cyrillic scripts.

In a survey conducted by researchers at Wichita State University, Calibri was the most popular font for e-mail, instant messaging and PowerPoint presentations. It also ranked highly for use in website text. The survey asked participants to rate images of sample text in various fonts.