Whether you're running an international championship race or out for a weekly jog, we all have a reason to run.
In London Marathon week, BBC Sport is launching the #IRunFor campaign for the 2017 summer of athletics.
The campaign will carry on across the World Athletics and Para Athletics Championships and beyond.
So, the next time you are pounding the streets think about why you do it, and be ready because we'll be asking you to be part of our #IRunFor campaign very soon.
And if you have good reasons but still haven't managed to take up running, we've got a guide to help you start.