A teacher from the Canadian Arctic has been named as the winner of the annual Global Teacher Prize.
Maggie MacDonnell, who teaches at a remote village school, spoke at the award ceremony about the problem of youth suicides in the Inuit community.
The winner was announced by a video-link with astronauts on the International Space Station.
She was congratulated by Canadian Prime Minister Justin Trudeau - who said she was "shaping the future".
"You chose to teach at the Ikusik school in Salluit, a remote village in the Canadian Arctic.
"There are no roads to Salluit - it is only accessible by air and it gets cold, really cold, -20c this time of year," said Mr Trudeau.
"I'd like to say thank you to every teacher out there."
Ms MacDonnell has worked to improve the health and life chances of an isolated community of young Inuit people who have faced deprivation - and she spoke of the impact on the community of high levels of youth suicides.
She described how it felt to be a teacher after the suicide of a student.
"As a teacher, when I come to school the morning after, there is an empty desk in that classroom. There is stillness and silence," she told the award ceremony.
Ms MacDonnell said the memory of such deaths haunted her and she wanted the prize to cast light on the problem.
"I didn't know until I came to Salluit that that was a Canadian reality," she said.
The $1m (£810,000) prize for teaching excellence was announced at the Global Education and Skills Forum in Dubai.
The prize is aimed at raising the status of teaching - with a show-business style ceremony with glamour and famous names.
The adventurer and TV presenter Bear Grylls and Italian singer Andrea Bocelli took part in the prize giving.
A video message from Prince Harry was screened and the ceremony was attended by the vice president of the United Arab Emirates, Sheikh Mohammad Bin Rashid Al Maktoum.
Astronaut Thomas Pesquet, speaking from the International Space Station, said: "I'd like to be the first person in history to thank all the world's teachers from space."
The top 10 finalists included a UK teacher, Raymond Chambers, who teaches computer science at Brooke Weston Academy, Corby, Northamptonshire.
Sunny Varkey, founder of the Varkey Foundation that organises the prize, said: "I hope Maggie MacDonnell's story will inspire those looking to enter the teaching profession and shine a powerful spotlight on the incredible work teachers do all over the world every day."
Aside from Maggie MacDonnell, the other finalists for the Global Teacher Prize 2017 were:
- Raymond Chambers, computer science teacher from Brooke Weston Academy, Corby, Northamptonshire, UK
- Salima Begum, head teacher at Elementary College for Women Gilgit, Pakistan
- David Calle, from Madrid, Spain, the founder and creator of the Unicoos educational website
- Wemerson da Silva Nogueira, a science teacher at the Escola Antonio dos Santos Neves in Boa Esperanca, Brazil
- Marie-Christine Ghanbari Jahromi, a physical education, maths and German teacher at Gesamtschule Gescher school, Germany
- Tracy-Ann Hall, an automotive technology teacher at Jonathan Grant High School in Spanish Town, Jamaica
- Ken Silburn, a science teacher at Casula High School, south-west Sydney, Australia
- Yang Boya, a psychology teacher at The Affiliated Middle School of Kunming Teachers College, China
- Michael Wamaya, a dance teacher from Mathare, Nairobi, Kenya