Players from Russia and Belarus are still permitted to compete on the tennis circuit, but must do so under a neutral flag.
The Toronto Open, which gets underway on Monday, is a WTA 1000 event and one of the biggest hard court tournaments of the summer.
“I wanted to inform you that unfortunately I have to withdraw from the tournament in Toronto due to my visa not being approved,” Azarenka said. “It’s truly disappointing. It’s very sad to miss one of my favorite tournaments.
“I love to play in Canada with great fans and a place where I made many friends over the years. Good luck to everyone at the event.
“See you in Cincinnati,” she ended, referencing the Cincinnati Masters which begins on August 13.
Tournament organizers Tennis Canada said in a statement: “Tennis Canada confirms that Victoria Azarenka has been unable to secure a visa in time to compete in the National Bank Open presented by Rogers.
“Tennis Canada has been working hard on the application with Vika and her team and have done everything we can to help but unfortunately the processing turnaround time has proved too challenging. We wish Vika all the best for the US hard-court season and hope to see her back in Canada next year.”
Azarenka is currently ranked 20th in the world and last week reached the quarterfinals of the Citi Open, losing to China’s Wang Xiyu in straight sets.