An OTMU file is a matrix template created by Origin 2018 and later, a data analysis and graphing application used by scientists and engineers in various fields. It contains matrix settings, which are used to create .OGMU graphs. OTMU files store one or more sheets, the number of rows and columns for each sheet, math functions, and the format and style.

OTMU files replaced .OTM files, which were used to save matrix templates in Origin before the release of Origin 2018. OTMU files are saved in a unicode format which features performance advantages over the older OTM file format. You can only open OTMU files with Origin, which can be used to create, open, and edit OTMU files. The program is only available for Windows. To open an OTMU file in Origin, select File → Open..., select the "Origin Template .otmu" file type, navigate to the OTMU file location, and click Open.