They last appeared on the red carpet together in April. An industry source told People that it was most likely their work that caused the breakup.
"Their work kept them apart a lot," they said. "Chicago Fire keeps him in Chicago and her work is almost always elsewhere."
Lady Gaga released a statement on Instagram shortly after the news about the breakup was released, saying that her and Taylor are 'having a break'.
She wrote: "Taylor and I have always believed we are soulmates. Just like all couples we have ups and downs, and we have been taking a break. We are both ambitious artists, hoping to work through long-distance and complicated schedules to continue the simple love we have always shared. Please root us on. We're just like everybody else and we really love each other."