The E351 series (E351系) was a tilting electric multiple unit (EMU) train type operated by East Japan Railway Company (JR East) on Chuo Main Line Super Azusa limited express services in Japan from 1993 to 2018. First introduced in December 1993 (initially on Azusa services), a total of 60 vehicles were built, formed as five eight-car main sets (numbers S1 to S5) and five four-car supplementary (numbers S21 to S25) sets.

Built jointly by Hitachi and Nippon Sharyo, the tilting E351 series trains were intended to replace the aging 183 series EMUs used on Azusa Limited express services operating between Shinjuku in Tokyo and Matsumoto, and to increase speeds on the highly curved Chūō Main Line.

At the time of withdrawal in 2018, the E351 series trains were used on the following services:

Other services previously operated by the series include:

The fleet consisted of five four-car sets (S21–S25) and five eight-car sets (S1–S5), formed as shown below, with car 1 (car 5) at the Shinjuku or Tokyo end.

When first delivered, the two pairs of sets were numbered and formed as shown below, with car 1 at the Shinjuku end.

Both standard class and Green (first) class seating were arranged 2+2 abreast.

E351 series trains were made entirely no-smoking on 18 March 2007.