The Spider is an American pulp-magazine hero of the 1930s and 1940s. The character was created by publisher Harry Steeger and written by a variety of authors for 118 monthly issues of The Spider from 1933 to 1943. The Spider sold well during the 1930s, and copies are valued by modern pulp magazine collectors. Pulp magazine historian Ed Hulse has stated "Today, hero-pulp fans value The Spider more than any single-character magazine except for The Shadow and Doc Savage."

The Spider was created in 1933 by Harry Steeger at Popular Publications as direct competition to Street and Smith Publications' vigilante hero the Shadow. Steeger said he got the idea for the character's name when he was playing tennis and saw a large spider walking along the edge of the court. Steeger also sought to emulate the films of Douglas Fairbanks, while historians George E. Turner and Michael H. Price felt the character was also descended from Siegfried, Fantômas and The Bat.

Recognizing that imitating the Shadow created the potential for lawsuits as well as the potential for strong sales, Streeger consulted his lawyer, who advised him to hire a writer with an established character and have him transform that character into the Spider. Thus, R.T.M. Scott's detective character Aurelius Smith and Hindu assistant Langa Doone became, respectively, Richard Wentworth and Ram Singh. The first two novels were written by R.T.M. Scott, but they were deemed too slow-paced, so another author was brought in. Later stories were published under the house pen name of "Grant Stockbridge", which was intended to recall Maxwell Grant, the house pen name which the Shadow novels were attributed to. Most of the Spider novels were actually written by Norvell Page. Other authors of the series included Donald C. Cormack, Wayne Rogers, Emile C. Tepperman, and Prentice Winchell. The series was the first Popular pulp to be named after a character rather than a genre.

The cover artists for The Spider magazine were Walter M. Baumhofer for the debut issue, followed by John Newton Howitt and Rafael De Soto. The Spider was published monthly and ran for 118 issues from 1933 to 1943. Sales declined in the late 1930s due to surging competition from superhero comics and (despite Spider novels making concessions to the popularity of superheroes, such as an increasing number of costumed villains) never fully recovered. Paper shortages during World War II and a declining readership following Page's departure to work on propaganda also played their part.

A 119th Spider novel manuscript (Slaughter Incorporated) had been completed but was not published until decades later (as Blue Steel), a heavily rewritten mass-market paperback with renamed characters. In 2012, Moonstone Books finally published it as Slaughter, Inc., in its original unedited form. The novel was again reprinted in 2018 by Altus Press as a facsimile edition, this time designed to look like a 1940s pulp.

The Spider stories often involve a bizarre menace to the country and a criminal conspiracy. They were often extremely violent, with the villains engaging in wanton slaughter of thousands as part of sometimes nationwide crime sprees. Pulp magazine historian Ed Hulse noted that "Spider novel death tolls routinely ran into the thousands". The master criminal of the stories is usually unmasked only in the last few pages. The stories often end with Wentworth killing the villains and stamping their corpses' foreheads with his "Spider" mark.

Will Murray would note the character's brutality and willingness to kill criminals, even occasionally pre-emptively. Price and Turner also noted he was considerably more brutal and violent than other pulp heroes, especially under Page, who they stated "maintained in the character a viciousness that placed The Spider magazine in a par with the horror-anthology pulps of its day".

A complete list of all 119 Spider pulps in the original series is available online at fan sites (see The Spider | List.)