The actor's husband Ben Daniels announced the news by sharing it on Instagram. Ian, best known for his role as Kevan Lannister in the legendary series, was diagnosed with bile duct cancer in December.
In an Instagram post shared with Gelder, Daniels wrote: "I dropped everything to take care of him, but neither of us knew it would happen so fast. He was the kindest, most generous-spirited and loving person alive. For over 30 years we were partners in this life. Even if we weren't together, we talked to each other every day. He was a great actor and everyone who worked with him was touched by his heart and his light. I don't know what I would do without him. He dealt with his terrible illness with great courage, without self-pity. Without stopping."
