Jar of Flies is a studio EP, released on January 25, 1994, by the Seattle, Washington rock band Alice in Chains through Columbia Records. Jar of Flies marks the first album with bassist Mike Inez. This album was the first EP to ever reach No. 1 on the Billboard 200 United States album chart, and was the only EP to ever gain this distinction until the 2004 release of the Linkin Park/Jay-Z collaboration enititled Collision Course. The EP features Alice in Chains' most radio successful song and two more successful singles for the band. The song "No Excuses" was the only Alice in Chains song to reach the number 1 position on the Billboard Mainstream Rock Tracks chart. "I Stay Away" also reached high positions, and "Don't Follow" had become a modest hit by early 1995.

Lyrical themes explored on Jar of Flies include drug use, relationships, and love. Most of the lyrics on the album are centered around drug use, due to singer Layne Staley's battle with heroin and other drugs, which would lead to his death in 2002. The lead single, "No Excuses", is about Staley's failed attempt with drug rehab.

According to lead singer Layne Staley, the title for the album came from a science experiment guitarist Jerry Cantrell conducted in third grade: "They gave him two jars full of flies. One of the jars they overfed, the other jar they underfed. The one they overfed flourished for a while, then all the flies died from overpopulation. The one they underfed had most of the flies survive all year. I guess there's a message in there somewhere. Evidently that experiment had a big impact on Jerry." .

In 1995, the album was briefly re-released in a limited edition, short-lived format called CD Plus. It contained a 2nd CD of drivers in order to access special computer content on the CD. The key extras were lyrics, discography and the full versions of both of the videos released from the EP, 'I Stay Away' and 'No Excuses'. The picture on the CD itself is the purple/orange photo negative of the one found on the regular release CD.

In addition to the CD, the album was also released in a limited edition double vinyl along with Sap. Jar of Flies was on sides 1 and 2, Sap was on side 3, and an etching of the Alice in Chains logo was on side 4.

The first pressing of the CD contained plastic flies in the spine of the jewel case.