In whose field did Ruth happen to glean grain?

Answer: Boaz

Ruth happened to come to the part of the field belonging to Boaz, who was from the clan of Elimelech.

“So Ruth departed and went out into the field and gleaned after the harvesters. And she happened to come to the part of the field belonging to Boaz, who was from the clan of Elimelech.”— Ruth 2:3 (BSB)