The 2018 Okayama GT 300km was the first round of the 2018 Super GT Series. It was held at the Okayama International Circuit in Mimasaka, Okayama Prefecture, Japan. The GT500 category was won by Koudai Tsukakoshi and Takashi Kogure in the #17 Honda NSX-GT, whilst Yuhki Nakayama and Takashi Kobayashi won the GT300 category in the #18 Team UpGarage Toyota 86.