An OTWU file is a workbook template created by Origin 2018 and later, a data analysis and graphing application used by scientists and engineers in various fields. It contains the layout settings for one or more worksheets, which include the number of rows and columns, added notations, and theme. OTWU files are used to create .OGWU workbooks.

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