Hannah O'Neill commenced ballet lessons as a three year old at the Kishibe Ballet Studio in Tokyo, Japan where she was born. In 2000 Hannah and her family moved to Auckland, New Zealand where she continued her training at the Mt Eden Ballet Academy.
In 2007 Hannah competed in the Youth America Grand Prix in New York and was awarded a fulltime scholarship to attend the Australian Ballet School. In 2008 at the age of 15 Hannah moved to Melbourne to begin fulltime training at the school. In 2009 Hannah was chosen to represent the Australian Ballet School at the prestigeous Prix de Lausanne where she was awarded First place.
The following year, 2010, Hannah once again competed at the Youth America Grand Prix and was awarded First Place in the senior womens section.
Having been named Dux, Hannah graduated from the Australian Ballet School in 2011 and immediately joined the Opera Nationale de Paris on a seasonal contract for two seasons.
In 2013 she joined the Corp de Ballet and within three months of joining the company was promoted to Coryphee.
In 2014 Hannah was awarded the Silver medal at the Varna International Ballet Competition and the Prix de dance de Cercle Carpeaux by the Paris Opera Ballet Company.
In 2015 Hannah was promoted to Sujet and in 2016 to Premiere Danseuse as well as being the recipient of the Prix de L'Arop.