Feeling stagnant in current role? How did you fix it?

I've been in my current role for a few years now, and I'm starting to feel a bit stagnant. I'm craving a new challenge, but I'm not sure if that means changing jobs or just shaking things up in my current position.

Have any of you successfully reinvented yourselves within the same company? How did you approach that conversation with your boss? Any advice for breathing new life into a job that's gone stale?