A low-cost carrier or low-cost airline (also known as a no-frills, discount or budget carrier or airline or cheap flight) is an airline that generally has lower fares and fewer comforts. To make up for revenue lost in decreased ticket prices, the airline may charge for extras like food, priority boarding, seat allocating, and baggage etc.

The term originated within the airline industry referring to airlines with a lower operating cost structure than their competitors. While the term is often applied to any carrier with low ticket prices and limited services, regardless of their operating models, low-cost carriers should not be confused with regional airlines that operate short flights without service, or with full-service airlines offering some reduced fares.

In due course, some airlines have actively sought to market and advertise themselves as low-cost, budget, or discount airlines while maintaining products usually associated with traditional mainline carrier's services which often result in increased operational complexity. Among these products which tend increase complexity to reduce efficiency are preferred or assigned seating, catering other items rather than basic beverages, differentiated premium cabins, satellite or ground based wifi internet, and in-flight audio video entertainment. As such by advertising themselves as low-cost, this branch and category of airlines seek to gain a competitive marketing advantage over other similarly priced air transportation carrier's products; even though in actuality fare prices for the passenger may be parallel to other airline options due to the associated add-on fees low-cost, discount, or budget; are increasingly accessing travlers to appear less expensive than traditional network or airline alliance linked carriers.