Epsilon no Fune (イプシロンの方舟, Ark of Epsilon) is the fourth studio album by Japanese singer Kotoko. It was released on October 14, 2009 by Geneon Entertainment. The album debuted at the sixth place of the Oricon daily charts, making this album one of the most successful in Kotoko's musical career. Overall, Epsilon no Fune is Kotoko's fourth best-selling album according to Oricon.
The album comes in a limited CD+DVD edition (GNCV-1014) and a regular CD-only edition (GNCV-1015). The DVD contains the PV and making for ε: Epsilon. Also, the album contained a special CD which contains a 2009 remix and the original version of her song Hitorigoto (ひとりごと, Soliloquy).