Natsumi Abe (安倍なつみ, born 10 August, 1981, in Hokkaido Prefecture) is a Japanese signer and actress and is a former member of Morning Musume. Her nickname is Nacci or Nacchi.

Natsumi was one of the first members of the group chosen in 1997. She was also the lead girl for many of the singles especially before Maki Goto joined, most notable in Furusato ('Hometown') where all the other girls sang harmonies/back-up only. Natsumi has had a few solo songs including the theme for a commercial she was in and Otoko Tomodachi from 4th Ikimasshoi. She also has lead roles in Morning Musume productions like their play, Love Century and their movie, Pinch Runner. Natsumi also has done quite a bit of acting in television dramas such as Nurseman.

Natsumi has never been a part of a subgroup but has lead each shuffle group she has been in. She was also the lead of Morning Musume Sakura Gumi until her graduation (at the end of the Hello! Project Winter tour on January 25th, 2004).

She released her first single, 22 sai no Watashi, on August 13, 2003, just a few days after her 22nd birthday. Her first full length CD was released shortly afterwards, containing many soloist versions of Morning Musume songs.

At one time, Natsumi was the most popular member of Morning Musume, and many songs featured her as a lead singer. However, it wasn't until the summer of 2003 that Natsumi officially went solo. Natsumi graduated shortly after that and continued to release more singles while actively participating in other Hello!Project activities such as concerts, the special soloist group Nochiura Natsumi (with Aya Matsuura and Maki Goto ), and the collaborative "All for One & One for All" (sang with all other soloists and groups within H!P at the time).

In late 2004, there was a plagarism scandal with some her essays and poems in her photobooks (which were copied off others' pieces) and she took a three-month personal leave, cease participation from all H!P-related activities (including Kaori Iida's graduation concert in January). She came back in February 2005 and will be participating in H!P activities once again (most notably Nochiura Natsumi's upcoming tour).