What is the name of the dot above the letter 'i'?

The name of the dot above the letter “i” is a tittle.

A tittle is the small superscript dot used above lowercase i and j in many Latin-script writing systems. It is technically a diacritic, but “diacritic” is the broader category, not the single canonical name for this particular mark.

The mark developed in medieval handwriting. It first helped distinguish the letter i from nearby vertical strokes, or minims, in sequences such as ii and later beside letters including m, n, and u. With the rise of Roman type, its shape became the familiar round dot.

The tittle is not universal. Turkish distinguishes dotted İ/i from dotless I/ı, which represent different sounds. When many accents are placed directly over i or j, the ordinary dot is usually removed, as in í or ĵ. The rare word also appears in the King James Bible’s phrase “one jot or one tittle.”