Sophie Kinsella — the powerhouse author behind the hit ‘Shopaholic’ book series — has died at 55, three years after being diagnosed with brain cancer.

The British writer’s family broke the heartbreaking news on her IG Wednesday … saying even though she battled her illness with unbelievable courage, she ultimately passed away peacefully … spending her final days wrapped in “family and music and warmth and Christmas and joy.”

Sophie first shared her cancer diagnosis just last April … revealing she had glioblastoma — the most aggressive form of brain cancer — but told fans she’d undergone a successful surgery and was pushing through radiotherapy and chemo.

Of course, Sophie is best known for her hit ‘Shopaholic’ series, which follows a retail-obsessed financial journalist — and later hit the big screen as “Confessions of a Shopaholic,” starring Isla Fisher.

Her most recent book, “What Does It Feel Like?,” dropped last year and was inspired by her own cancer journey.

She was 55.