"Sinister War" is a 2021 comic book storyline published by Marvel Comics, starring the character Spider-Man and written by Nick Spencer. The story deals with Spider-Man being in the middle of a conflict between multiple teams of villains, including the Sinister Six and Savage Six, orchestrated by Kindred. The storyline received mixed reviews from critics with many deeming it as an underwhelming conclusion to Nick Spencer's Spider-Man run due to inconsistent art, sluggish pacing, and Kindred.

Nick Spencer is a comic book writer and former politician best known for his Image series Morning Glories, his collaborations with artist Steve Lieber on the comedic series Superior Foes of Spider-Man and The Fix, a three-year run on Marvel's The Amazing Spider-Man, as well as his controversial Captain America storyline that began with Captain America: Sam Wilson, continued with Captain America: Steve Rogers, and culminated in the 2017 company-wide crossover "Secret Empire".