The Will of Fire (火の意志, Hi no Ishi) is a recurring element throughout the Naruto series. It is an ideal rooting from the belief of the Senju clan ancestor that love is the key to peace. It would eventually become the life philosophy which Hashirama and the Senju clan lived by, which has since been passed on to many ninja from Konohagakure as a part of their spiritual heritage. It states that every true Konoha shinobi must love, believe, cherish and fight for the village's sake, as previous generations had done before them. In Konoha, there is a sculpture of a flame in the cemetery representing this will, it has the kanji for "Hokage" (火影, Literally meaning: Fire Shadow) inscribed below it. Hashirama was also depicted sitting on a throne-like chair with a similar sculpture in the background.
According to Hiruzen Sarutobi, this is what gives Konohagakure shinobi the strength to continue fighting against all odds, building willpower and strength of character. It is also symbolic of the hopes and dreams of the previous generation being passed to the next; for example, when Asuma Sarutobi was killed, his hopes and dreams were passed to Shikamaru Nara, who asked that Asuma's will would in turn be passed on to his and Kurenai's child.
This is also seen with the shinobi of the village identifying a "King" (玉, Gyoku) which is simply anything or anyone they want to protect. When he was younger, Asuma Sarutobi was asked by his father who the 'King' was. Conflicted over whether it was the Daimyō of the Land of Fire or the Hokage, he was unable to answer him. Much later in his life, Asuma realised what his father meant and came to view his then unborn child as his 'King'. Shikamaru later came to realise that the 'King' was the unborn generations of Konohagakure to come, and Konohamaru Sarutobi believes that they are the civilians of the village that cannot fight for themselves.
- It has been noted that the Uchiha clan's Curse of Hatred (憎しみの呪い, Nikushimi no Noroi) is fated to clash against the Will of Fire, and Obito believes that Sasuke Uchiha and Naruto Uzumaki, both respectively embodying the polar ideals, are destined to fight to the death.
- Iwagakure has a similar philosophy known as the "Will of Stone" (石の意志, Ishi no Ishi)..
- Some notable Uchiha have been able to transcend the limitations of their clan-thinking and held the Will of Fire philosophy such as Itachi, Shisui, and Kagami. Obito Uchiha also held to such beliefs in his youth. Most recently, Sasuke Uchiha who was seemingly lost to the Curse of Hatred has also seemingly come to believe in this philosophy.
- Kakashi theorised that Obito, despite succumbing to his clan's hatred, never truly lost his Will of Fire, and the two conflicting ideals were tearing him up inside.