Astellas Pharma Inc. (アステラス製薬株式会社, Asuterasu Seiyaku Kabushiki-gaisha) (TYO: 4503) is a Japanese pharmaceutical company, formed on 1 April 2005 from the merger of Yamanouchi Pharmaceutical Co., Ltd. (山之内製薬株式会社, Yamanouchi Seiyaku Kabushiki-gaisha?) and Fujisawa Pharmaceutical Co., Ltd. (藤沢薬品工業株式会社, Fujisawa Yakuhin Kōgyō Kabushiki-gaisha?).