Serious Request is a family of annual multi-day, multimedia fundraising events for International Red Cross initiatives, typically hosted by radio stations in the week before Christmas. The project was begun in 2004 by Dutch public pop music radio station 3FM. Serious Request projects have since been adopted in Belgium, Switzerland, Sweden, Kenya, South Korea, Austria, Latvia and Portugal.

The DJs make an interactive, themed broadcast around the clock, while regular programming on the station is suspended. Instead, 3FM and its website are completely dedicated to the event, which is also transmitted as a continuous audio and video live-stream. Additionally, there is television coverage, integration with social media, and a dedicated mobile app.

Funds are raised in a few different ways. DJs play songs requested by listeners and visitors, in return for their donations. Celebrities and artists also donate personal possessions or offer unique opportunities to meet them, which are auctioned off. Straightforward donations are made into the project's bank account, and by physical visitors depositing cash and cheques into the house's letterbox. Additionally, members of the public run a variety of supporting initiatives, and in some cities, more glass houses are popping up. All totalled, the Dutch editions have raised €76.8 million through 2014, with total donations in some editions exceeding 10 million euros.

During the Dutch 3FM Serious Request, three radio DJs of the national channel (NPO) 3FM were locked up for six days in a small temporary radio studio (the "Glass House") until 2018. It was placed in a main square in a different city each year. They weren't allowed to eat anything; instead, they drank water, juice, and other liquids to stay energized.

In the Netherlands, the Serious Request broadcasts and the Glass House became a national December tradition, that reaches most of the national population. The 2012 edition was watched and listened to by 12.1 million people over the age of ten, or 84% of Dutch people in that age group. Overall, 88% of the people were aware of the event.

From 2016 on, however, the general public's interest in the event, and therefore donations, were declining. From 2018 on, 3FM decided to abolish their Glass House and tried to bring the event closer to the people by sending DJs of the radio station to travel the country on foot. The new formula is called The Lifeline.