You don't reference the speech itself, but rather the source you found the speech in, for example, a book, video recording, or website. Even for a very famous speech you should find an authoritative source to reference.
To reference a speech transcript, please refer to the link below.
The in-text citation would include the surname of the author (or editor) of the source document and the year of publication (not the speaker's name or the year he/she made the speech). The reference list would include all information appropriate for the source document.
