* As a pronoun: "I" is a personal pronoun, referring to the speaker. In this case, it's not a noun.
* As a noun: "I" can sometimes be used as a noun, particularly when referring to the letter "I". For example: "The letter I is a vowel."
Let me know if you have a specific sentence in mind, and I can tell you for sure whether "I" is a noun or a pronoun!