Cannot find Microsoft.Office.Interop Visual Studio

If you're using Visual Studio 2015 and you're encountering this problem, you can install MS Office Developer Tools for VS2015 here.

Look for them under COM when trying to add the references. You should find the reference below, and possibly Microsoft Outlook 15.0 Object Library, if you need that. There are similar libraries for Word, Excel, etc.:

Update: The Object Library should contain the Interop stuff. Try to add this to a source file and see if it can now find what you need:

using Microsoft.Office.Interop.Outlook;

I forgot to select Microsoft Office Developer Tools for installation initially. In my case Visual Studio Professional 2013 and also 2015.