1. Uchiha Fugaku: Fugaku, head of the Uchiha clan, played a significant role in Itachi's development as a ninja. He taught Itachi various ninja techniques and fundamental skills.

2. Suigetsu: Suigetsu was Itachi's Genin partner. Their companionship was invaluable for Itachi's personal growth and understanding of life.

3. Uchiha Shisui: Shisui greatly influenced Itachi's life. He acted as an older brother, a friend, and a teacher to Itachi. Shisui was the only person who truly understood Itachi and his self-deceptive nature. He entrusted Itachi with his Mangekyou Sharingan and the power of Izanami.

4. Uchiha Obito: Disguised as Uchiha Madara, Obito initially killed Itachi's teammate, Izumi Uchiha. This triggered Itachi's awakening of the Mangekyou Sharingan. Itachi later sought Obito's help to infiltrate the Akatsuki organization. Itachi considered Obito a legendary figure and his former teacher, but also remained wary of his true intentions.