lyricist; songwriter; lyric writer
Refers specifically to the person who writes the lyrics for a song, as opposed to the composer (作曲者).
She is a famous lyricist.
Who is the lyricist for this song?
作詞家 is a more common and slightly more professional-sounding term for a lyricist; 作詞者 is also used but may sound more formal or technical.
Compound of 作詞 (sakushi, 'lyric writing') + 者 (sha, 'person').