In business, a unicorn is a startup company valued at over US$1 billion which is privately owned and not listed on a share market. The term was first published in 2013, coined by venture capitalist Aileen Lee, choosing the mythical animal to represent the statistical rarity of such successful ventures.

Many unicorns saw their valuations fall in 2022 as a result of an economic slowdown caused by the COVID-19 pandemic, an increase in interest rates causing the cost of borrowing to grow, increased market volatility, stricter regulatory scrutiny and underperformance. CB Insights identified 1,248 unicorns worldwide as of May 2024^[update]. Unicorns with over $10 billion in valuation have been designated as "decacorn" companies. For private companies valued over $100 billion, the terms "centicorn" and "hectocorn" have been used.

Aileen Lee originated the term "unicorn" in a 2013 TechCrunch article, "Welcome To The Unicorn Club: Learning from Billion-Dollar Startups". At the time, 39 companies were identified as unicorns. In a different study done by Harvard Business Review, it was determined that startups founded between 2012 and 2015 were growing in valuation twice as fast as startup companies founded between 2000 and 2003.

In 2018, 16 US companies became unicorns, resulting in 119 private companies worldwide valued at $1 billion or more. Globally, according to CB Insights, there were more than 803 unicorns as of August 2021^[update], with ByteDance, SpaceX and Stripe among the largest, and 30 decacorns, including SpaceX, Getir, Goto, J&T Express, Stripe, and Klarna.

The surge of unicorns was reported as "meteoric" for 2021, with $71 billion invested in 340 new companies, a banner year for startups and for the US venture capital industry; the unprecedented number of companies valued at more than $1 billion during 2021 exceeded the sum total of the five previous years. Six months later, in June 2022, 1,170 total unicorns were reported. IPL with $10.9 billion made into decacorn in 2022. The growth of unicorns has slowed more recently with 1248 total unicorns reported in May 2024.

During the mid-2000s, investors and venture capital firms were adopting first-mover advantage and get-big-fast (GBF) strategies for startups, also known by the neologism, "blitzscaling". GBF is a strategy where a startup tries to expand at a high rate through large funding rounds and price cutting to gain an advantage on market share and push away rival competitors as fast as possible. The rapid returns through this strategy seem to be attractive to all parties involved, despite the cautionary note of the dot-com bubble of 2000, as well as a lack of long-term sustainability in value creation of emerging companies of the Internet age.

Many unicorns were created through buyouts by large public companies. In a low-interest-rate and slow-growth environment, many companies like Apple, Meta, and Google focus on acquisitions instead of focusing on capital expenditures and development of internal investment projects. Some large companies would rather bolster their businesses through buying out established technology and business models rather than creating it themselves.

The average age of a technology company before it goes public is 11 years, as opposed to an average life of 4 years back in 1999. This new dynamic stems from the increased amount of private capital available to unicorns and the passing of the US's Jumpstart Our Business Startups (JOBS) Act in 2012, which increased by a factor of four the number of shareholders a company can have before it has to disclose its financials publicly. The amount of private capital invested in software companies has increased three-fold from 2013 to 2015.