Miss Lambie (24), who was born and raised in Dunedin, beat 18 other contestants.
''I still can't really believe it,'' she said last night.
The competition, judged over three months, included a sports day, speeches, interviews, and a talent event, and culminated in Auckland on Saturday night.
Miss Lambie won the sports day by completing challenges including the most press-ups, sit-ups and burpees in a given time.
The competition also included her doing a rhythmic gymnastics routine and answering a question about how to combat Islamic State.
The former Columba College pupil was excited by being given the chance to represent Otago and New Zealand at Miss World in November.
''It's the biggest beauty pageant in the world.''
The dates and the host country were yet to be confirmed but there had been bids by Australia. the Philippines and Bali.
A New Zealander had never won the Miss World contest and she was preparing to give it her best shot, she said.
''The hard work starts now.''
Miss Lambie is in her final year of study and will graduate as a doctor in December.
