Kōji (弘治?) was a Japanese era name (年号 nengō?, "year name") after Tenbun and before Eiroku. This period spanned the years from October 1555 through February 1558. Reigning emperors were Go-Nara-tennō (後奈良天皇?) and Ōgimachi-tennō (正親町天皇?).
The name originates from the following Chinese passage: 「祇承宝命、志弘治体」.