Karl Martin Sandberg (born 26 February 1971), known professionally as Max Martin, is a Swedish record producer and songwriter. He rose to prominence in the late 1990s with songwriting credits on a string of hit singles, such as Britney Spears's "...Baby One More Time" (1998), the Backstreet Boys' "I Want It That Way" (1999), Celine Dion's "That's the Way It Is" (1999) and NSYNC's "It's Gonna Be Me" (2000).

Martin has written or co-written 27 Billboard Hot 100 number-one singles; 25 of which he has produced or co-produced, an all-time record for the chart as of March 2024. His credits include Katy Perry's "I Kissed a Girl" (2008) and "Roar" (2013), Maroon 5's "One More Night" (2012), Taylor Swift's "Shake It Off" and "Blank Space" (2014), and the Weeknd's "Can't Feel My Face" (2015), "Blinding Lights" (2019) and "Save Your Tears" (2020). "Blinding Lights" is the best performing song of all time according to the chart. Martin has written the second-most number-one singles on the chart, behind only Paul McCartney (32), having surpassed John Lennon (26) with his 27th number one in March 2024. Many of Martin's hits were used in the 2019 jukebox musical & Juliet.

In early 2013, The Hollywood Reporter tallied his singles sales at over 135 million copies. According to Variety, his net worth was approximately $260 million in 2017; the previous year, his corporate entity generated revenue of $54 million with a profit of $19 million. Martin has won the ASCAP Songwriter of the Year award for a record of 11 times. He has also won five Grammy Awards, including Producer of the Year, and nominations for an Academy Award and two Golden Globe Awards.