the previous week; the week before
Refers to the week immediately before a reference point in time. Often used in narratives or when comparing schedules.
I still haven't read the book I bought the previous week.
This week is busy, but the week before was even tougher.
A straightforward phrase composed of 前 (まえ, 'before') + の (possessive particle) + 週 (しゅう, 'week').