Agile software development is an umbrella term for approaches to developing software that reflect the values and principles agreed upon by The Agile Alliance, a group of 17 software practitioners, in 2001. As documented in their Manifesto for Agile Software Development, the practitioners value:

The practitioners cite inspiration from new practices at the time including extreme programming, scrum, dynamic systems development method, adaptive software development, and being sympathetic to the need for an alternative to documentation-driven, heavyweight software development processes.

Many software development practices emerged from the agile mindset. These agile-based practices, sometimes called Agile (with a capital A), include requirements, discovery, and solutions improvement through the collaborative effort of self-organizing and cross-functional teams with their customer(s)/end user(s).

While there is much anecdotal evidence that the agile mindset and agile-based practices improve the software development process, the empirical evidence is limited and less than conclusive.

Iterative and incremental software development methods can be traced back as early as 1957, with evolutionary project management and adaptive software development emerging in the early 1970s.

During the 1990s, a number of lightweight software development methods evolved in reaction to the prevailing heavyweight methods (often referred to collectively as waterfall) that critics described as overly regulated, planned, and micromanaged. These lightweight methods included: rapid application development (RAD), from 1991; the unified process (UP) and dynamic systems development method (DSDM), both from 1994; Scrum, from 1995; Crystal Clear and extreme programming (XP), both from 1996; and feature-driven development (FDD), from 1997. Although these all originated before the publication of the Agile Manifesto, they are now collectively referred to as agile software development methods.

Already since 1991 similar changes had been underway in manufacturing and management thinking derived from Lean management.

In 2001, seventeen software developers met at a resort in Snowbird, Utah to discuss lightweight development methods. They were: Kent Beck (Extreme Programming), Ward Cunningham (Extreme Programming), Dave Thomas (Pragmatic Programming, Ruby), Jeff Sutherland (Scrum), Ken Schwaber (Scrum), Jim Highsmith (Adaptive Software Development), Alistair Cockburn (Crystal), Robert C. Martin (SOLID), Mike Beedle (Scrum), Arie van Bennekum, Martin Fowler (OOAD and UML), James Grenning, Andrew Hunt (Pragmatic Programming, Ruby), Ron Jeffries (Extreme Programming), Jon Kern, Brian Marick (Ruby, Test-driven development), and Steve Mellor (OOA). The group, The Agile Alliance, published the Manifesto for Agile Software Development.