An .Rproj file is a project file used by RStudio to organize and manage R work. Open it by double-clicking the file on your computer—this will launch RStudio automatically and load the project with all its settings and file structure. Alternatively, open RStudio first, then use File > Open Project and navigate to the .Rproj file. You can also open it from the command line by running open projectname.Rproj (macOS), start projectname.Rproj (Windows), or xdg-open projectname.Rproj (Linux). When a project opens, RStudio restores your previous working directory, loaded scripts, environment variables, and other session settings. This makes it easy to pick up where you left off on a specific analysis or project. Note that you need RStudio installed on your computer to open .Rproj files directly—they won't open with standard text editors or R alone, though you can view the file's contents (it's a plain text configuration file) in any text editor if needed for troubleshooting.