The 25-year-old singer hinted the huge design is set to get bigger as it is only half-completed.
Posting a photo of the mammoth tattoo on Instagram, he wrote, "Halfway and ouch (sic)."
Later, Sheeran tweeted confirming celebrity tattoo artist Kevin Paul had worked on the intricate design and thanked him for dealing with his moaning.
"Lion is courtesy of @kp_est78, who puts up with me complaining about the pain (sic)," he wrote.