G-Eazy Denied Entry into Canada for Headlining Concert

G-Eazy was just turned away at the Canadian border ... and had to cancel a huge show because of it.

Sources tell us G-Eazy and crew ran into issues with Canadian customs agents when they touched down in Calgary Monday. The rapper was set to be a headliner at the Cowboys Music Festival ... a festival that coincides with the Calgary Stampede.

The Cowboys Dance Hall released a statement Monday night, saying, "Cowboys regrets to inform you that G-Eazy is unable to perform tonight due to reasons beyond our control. Refunds will be processed at the online point of purchase (Showpass)."

It's unclear exactly why G-Eazy was rejected -- but Canada has pretty strict entry rules -- so there's a good chance his recent cocaine arrest in Sweden had something to do with it.