Henry Russell Walter (born April 23, 1986), known professionally as Cirkut, is a Canadian record producer and songwriter. He has produced and co-written commercially successful singles since 2008. His credits include songs and albums for prominent artists including Katy Perry, Becky G, Ava Max, Nicki Minaj, Lady Gaga, Charli XCX, R. City, The Weeknd, Kesha, Ciara, Pitbull, Britney Spears, Maroon 5, Ne-Yo, Rihanna, Adam Lambert, B.o.B, Marina and the Diamonds, will.i.am, Jungkook, Kygo, Juicy J, Sam Smith, and Ed Sheeran, among others. He has numerous collaborations with American record producer Dr. Luke and Swedish producer Max Martin.
Walter has written and produced the Billboard Hot 100-number one singles "Part of Me", "Roar" and "Dark Horse" by Katy Perry, "Wrecking Ball" by Miley Cyrus, "Girls Like You" by Maroon 5, and "Starboy" and "Die for You (Remix)" by the Weeknd. He co-produced Jungkook's 2023 single "Standing Next to You". He has co-written and produced every song on Becky G's Play It Again, R. City's What Dreams Are Made Of, Ava Max's Heaven & Hell and Diamonds & Dancefloors, and Lady Gaga's Mayhem.
Walter has won three Grammy Awards, including Best Urban Contemporary Album for the Weeknd's Starboy, Best Dance Pop Recording for Lady Gaga's "Abracadabra", and was named the 2026 Producer of the Year.
Walter was born in Ottawa and mostly lived in Montreal. In his teenage years he had moved to Halifax where he attended Armbrae Academy and St. Pat's High School in Halifax, Nova Scotia where he met some other musical artists. He then moved to Toronto in 2004. He co-produced the Britney Spears song "Mmm Papi" which appeared on her 2008 album Circus. He sent it as an instrumental track to Kobalt Music Group via their attorney Chris Taylor, where songwriter Nicole Morier began using it to write with Britney Spears.
Walter opened Dream House Studios in Toronto. He then relocated to Los Angeles, California. He co-produced "Part of Me", the title song to Katy Perry's 2012 concert film '. Walter was also responsible for producing and co-writing the Weeknd's track "High for This". In 2016, he co-produced and co-wrote 9 songs on the Weeknd's album Starboy.
|- ! scope="row" | | "Roar" | Song of the Year | |- ! scope="row" | | Starboy | Best Urban Contemporary Album | |- ! scope="row" | | Donda | Album of the Year | |- ! scope="row"| | "Higher than Ever Before" | Best Dance/Electronic Recording | |- ! scope="row" rowspan="2"| | Brat | Album of the Year | |- | "360" | Record of the Year | |- ! scope="row" rowspan="7"| | Mayhem | Album of the Year | |- | rowspan="3"| "Abracadabra" | Record of the Year | |- | Song of the Year | |- | Best Dance Pop Recording | |- | rowspan="2"| "APT." | Record of the Year | |- | Song of the Year | |- | Himself | Producer of the Year, Non-Classical |