Futari Ecchi (Japanese: ふたりエッチ, Hepburn: Futari Etchi) is a Japanese manga series written and illustrated by Katsu Aki. It has been serialized in Young Animal since December 1996, with the chapters later combined into tankōbon volumes by Hakusensha, of which there are eighty-nine as of May 2023. The series follows a newlywed couple in their mid-twenties, both virgins when they married, and chronicles their sexual explorations. The manga combines erotic elements with factual and informative statistics. Its title Futari Ecchi ("two person ecchi") is a play on a slang term for masturbation, hitori ecchi ("single person ecchi"). The series has 29.5 million copies in print and is most famous for being a how-to guide combined with a story.Two spin-off manga have been released, Futari Ecchi for Ladies focusing on the sexuality of women and Futari Ecchi Gaiden: Akira, The Evangelist of Sex focusing on Akira. There are also two sex manuals and an art book. The series was adapted into a three episode live-action television drama that aired on WOWOW in 2000. A four-volume original video animation (OVA) series was produced from 2002 and 2004. In 2011, a twelve-episode live-action web series was streamed on Ustream. Also in 2011, a live-action theatrical film series began. Four films have been released. A second three episode OVA series was released in 2014 by Production Reed.

In 2007, the manga series was licensed in North America by Tokyopop as Manga Sutra, only four volumes were released, comprising eight Japanese volumes. Also in 2007, Media Blasters licensed and released the OVAs on DVD as Step Up Love Story.