South Africa captain Graeme Smith has revealed that family reasons played a part in his decision to retire from international cricket.

Smith made the announcement earlier this evening, bringing an end to an illustrious career in which he became the most successful Test captain of all time and scored more than 17,000 runs.

The 33-year-old said that he had been considering retirement since undergoing ankle surgery in April of last year and believes that doing it after the third Test against Australia at Newlands is as good a time as any.

"This has been the most difficult decision I have ever had to make in my life. It's a decision that I have been considering since my ankle surgery in April last year," Smith told Cricket South Africa's website.

"I have a young family to consider, and I felt that retiring at Newlands would be the best way to end it because I have called this place home since I was 18 years old. I have always been someone who has left everything out there on the field for my team and for my country.

"I'm extremely honoured and proud to have had the privilege to lead so many wonderful players and to have been a part of building the Proteas culture to what it is today. It is a culture that every player can be, and is, immensely proud of."

Smith was also keen to thank those who had helped him throughout his career and singled out guiding South Africa to the top of the world rankings as one of his proudest moments.

"I would like to express my deepest gratitude to the support from my parents and brother, my wife and children, my friends, my sponsors, my fans and to Cricket South Africa," he added.

"I thank and honour the players who I have played with and those who have supported me and helped me to be the person and captain I am today. I have been fortunate to have had many highs, amongst them leading and being part of the best Test team in the world.

"I will cherish these memories for the rest of my life. Thank you from the bottom of my heart. I bid my career a fond yet sad farewell."

South Africa are currently trailing Australia by 234 runs after day three of their third and final Test.