|This article is about the Story Library book. You may be looking for the fifth season song, the annual story, the Engine Adventures book, the helicopter or the ancient Sudrian king.|
Harold (later re-titled Percy and Harold's Big Race) is the twenty-third book in the My Thomas Story Library series.
Harold boasts that he can go faster than steam engines, but Percy soon proves him wrong with a race to the harbour.
- This book is based on the story, "Percy and Harold" from the Railway Series book, Percy the Small Engine.