For 10 years, Secretary-General Ban Ki-moon has served as the head of the United Nations and the world’s top diplomat. As his tenure comes to a close at the end of December, the United Nations Foundation is expressing our gratitude for his decade of global leadership. For the past 10 years, he has been a relentless advocate for sustainable development, climate action, gender equality, and a more peaceful, secure world. We have been privileged to work with him and look forward to continuing our support of the United Nations as António Guterres takes office in 2017. Here is a look at the legacy Secretary-General Ban leaves.