|Ami Mizuno||Act 2||Ep. 8||Act 1|
|Sailor Mercury||Act 2||Ep. 8||Act 2|
|Dark Mercury||--||--||Act 21|
|Super Sailor Mercury||Act 35||Ep. 143||--|
|Princess Mercury||Act 41||--||--|
|Third Senshi form||Act 42||--||--|
Ami's Senshi identity is Sailor Mercury. She wears a uniform colored in shades of blue, and is given specific titles throughout the various series. These include Soldier of Water and Intelligence, Soldier of Wisdom, Soldier of Justice and Wisdom, and Soldier of Love and Exams. Her personality is no different from when she is a civilian, although certain powers are unavailable to her in that form.
In Japanese, the name for the planet Mercury is Suisei (水星), the first kanji meaning 'water' and the second indicating a celestial object. Although the Roman planet-name is used, Sailor Mercury's abilities are water-based due to this aspect of Japanese mythology. Initially most of her powers are strategic rather than offensive, and she possesses various pieces of computerized equipment to help her study the enemy.
As she grows stronger, Sailor Mercury gains additional powers, and at key points her uniform changes to reflect this. The first change takes place in Act 35 of the manga, when she obtains the Mercury Crystal and her outfit becomes similar to that of Super Sailor Moon. She is not given a new title. A similar event is divided between episodes 143 and 151 of the anime, and she is given the name Super Sailor Mercury. A third, manga-only form appears in Act 42, unnamed but analogous to Eternal Sailor Moon (sans wings).