Henry Russell Walter, known professionally as Cirkut, is a Canadian record producer and songwriter. Described by The Hollywood Reporter as record producer Dr. Luke's "right-hand man and main production partner", he has co-produced and co-written for Jessie J, Britney Spears, Kesha, Rihanna, Shakira, Nicki Minaj, B.o.B, Lil Wayne, and Taylor Swift, including the Billboard Hot 100 No. 1 singles, "Part of Me", "Roar", and "Dark Horse" by Katy Perry, and "Wrecking Ball" by Miley Cyrus.