The starry sky has been a source of inspiration throughout human history. Astronomy has been a common element in all cultures and civilizations, being used to establish calendars, navigate and discover new lands, and drive numerous scientific and technical breakthroughs. This Review discusses how it is becoming increasingly difficult for professional and amateur astronomers to observe the night sky because of light pollution. Artificial light at night, radio interference, and the deployment of satellite constellations are all rapidly increasing and are having adverse impacts on astronomical observations, limiting scientific discoveries, cultural connections to the night sky, and opportunities presented by astrotourism. Potential mitigation strategies to preserve the night sky are discussed.