Greta Thunberg is often the first name that comes up when people talk about the youth environment movement, but there are young activists all over the world.
From India to Kenya to USA young people have been demanding greater action on things like climate change, plastic pollution and deforestation.
On 20 September kids all over the world will be taking part in the Global Climate Strike, and you can keep up with everything that's going on in our live page here.
Then on 21 September young leaders and activists from around the world including Greta Thunberg gather at the UN's Youth Climate Summit in New York.
Here are some of the people who are taking part in the movement to inspire change around the world.
Lesein Mutunkei (Kenya)
Lesein combined his love for the outdoors and football after hearing about deforestation, climate change and plastic pollution.
The 15 year old plants a tree for every goal he scores.
He encouraged his school and his football club to adopt an environmentally conscious attitude so that as they improve their football they also improve the environment.
Alexandria Villasenor (USA)
14-year-old Alexandria Villaseñor strikes outside the UN headquarters in New York every Friday.
The teenager, who is a Fridays For Future organiser, said: "I'm too young to vote. When I strike, I feel like I am taking back some agency in my future."
Aditya Mukarji (India)
Aditya, who is 15, started campaigning to get people to stop using plastic straws at the beginning of 2018.
At the age of 13 he went round cafes and restaurants persuading them to swop plastic straws for eco-friendly alternatives.
The teenager now promotes alternatives to plastic, campaigns against trees being cut down and supports the climate strikes.
Ella and Caitlin McEwan (UK)
Ella and Caitlin McEwan from Southampton are two sisters who made a petition asking fast food restaurants to stop putting plastic toys in kids' meals.
Ella and Caitlin gathered more than 400,000 signatures. Since then McDonalds said its customers would be able to choose between a toy and a fruit and Burger King said it will remove the plastic toys altogether.
Leah Namugerwa (Uganda)
Leah Namugerwa is a 14-year-old climate activist and student striker with Fridays for Future in Uganda.
She has been striking every Friday for greater action on climate change and plastic pollution since February 2019.
Her country, like many others in Africa, is at risk of desertification - that means fertile farming land turning dry and barren.
Experts say it's caused by droughts and raised temperatures - two factors linked to climate change.
"I wanted to make a positive change in my country and pressure my government into taking action," she told the BBC.
Lilly Platt (Netherlands)
Lilly Platt was born in Britain but lives in the Netherlands where at just 11 years old she has been striking every Friday for climate change.
Accompanied by her mum, she strikes on Fridays for an hour with permission from her school.
She is a child ambassador for the Plastic Pollution Coalition and HOW Global, a water charity.
And she has her own litter-picking campaign, Lilly's Plastic Pick Up. Started in 2015, when Platt was seven.
Holly Gillibrand (UK)
Holly Gillibrand leaves school for an hour every Friday to demand action on climate change.
Holly lives in Fort William which has a population of just 10,000 people. Around 40 people join her to protest every Friday,
"I want to get Scottish leaders to take climate change seriously and [know] that they're destroying my future," she told the BBC.
Source: BBC Newsround