"Brand New Day" is a comic book storyline in The Amazing Spider-Man, published by Marvel Comics beginning in 2008. It chronicles the start of Spider-Man's adventures in the aftermath of the status quo-altering "One More Day" storyline, and continues afterwards into "Spider-Man: Big Time".

Although the banner only runs across the front covers of #546–564 and the Spider-Man: Swing Shift (Director's Cut) one-shot (itself a reprint, with new material, of the Free Comic Book Day 2007: Spider-Man one-shot), "Brand New Day" is also used to refer to the entire 102-issue run of stories featured in The Amazing Spider-Man #546–647 and accompanying tie-in series, one-shots, and annuals.

During this time, Marvel made The Amazing Spider-Man the company's sole Spider-Man title, upping its frequency of publication to three issues monthly and cancelling the other then-current Spider-Man titles The Sensational Spider-Man and Friendly Neighborhood Spider-Man, and inaugurated the series with a sequence of "back to basics" story arcs. This marks the first time since December 1976 (when Peter Parker, The Spectacular Spider-Man #1 was published) that only one regularly published title featured Spider-Man in its title.

Following the events of "One More Day", Spider-Man's marriage to Mary Jane Watson has been erased, resulting in adjustments to his own history. Spider-Man's secret identity has also been forgotten by everyone, including people who knew his identity before his public unmasking. Harry Osborn is again alive; he has been living in Europe for several years. Aunt May is alive and well and volunteers in a homeless shelter. Peter has his original mechanical webshooters. Although "some people" vaguely recall that Spider-Man unmasked himself during the events of Civil War, they do not remember whose face was under the mask, and even if this is brought to their attention, they soon cease to worry about it.

Spider-Man has not been seen for one hundred days due to the implementation of the Superhuman Registration Act. In the meantime, Peter Parker has been residing at Aunt May's house as he searches for an affordable apartment. Feeling concerned, Peter decides to visit the Daily Bugle and is shocked to learn about the publication's severe financial troubles. Unfortunately, the stress takes a toll on J. Jonah Jameson, who suffers a heart attack.

In light of the Bugle's financial difficulties, Robbie Robertson asks Peter to do what he can to get Spider-Man pictures that he believes would boost circulation, which convinces Peter to return to the web-slinging. Robbie is finally getting on top of things as Dexter Bennett, a celebrity businessman, arrives to inform him that he's bought all of Jameson's Bugle shares and is now running operations.

After encountering supervillain Menace, Peter is concerned that Harry might have returned to his goblin-glider ways, but Harry's girlfriend, Lily Hollister, provides an alibi.

It is established that Mary Jane and Peter were in a long-term relationship, but things ended badly, and their relationship is now frosty at best. As far as Peter (or anyone else) remembers, he and Mary Jane did not get married, but cohabited as a couple since the day of the aborted wedding. It is unclear whether Mary Jane has an awareness of her previous marriage to Peter, and their deal with Mephisto.