A Number-One Hit is a song that has charted #1 in the official weekly single chart of a country.
To make sure you have correct information, please use these websites:
-  (UK Top 40)
-  (Billboard Hot 100 for the USA)
-  (charts for Australia, Austria, Denmark, France, Netherlands, New Zealand, Norway, Sweden and Switzerland)
-  (charts for Argentina, Brazil, Bulgaria, Canada, Chile, China, Greece, Hungary, India, Ireland, Italy, Japan, Portugal, Russia, Spain, Taiwan and Ukraine)
-  (German chart)