parent-in-law; parents-in-law
Refers to one's spouse's parent(s). The term is neutral and commonly used in family contexts.
I live with my parents-in-law.
Meeting my parent-in-law for the first time makes me nervous.
Specifically 'father-in-law', while 義理の親 is a broader term.
Compound of 義理 (giri, 'duty' or 'in-law relationship') and 親 (oya, 'parent'). The phrase directly means 'parent by marriage'.