40 Days for Life is an international, religiously-based  pro-life advocacy group that campaigns against abortion in over 20 nations worldwide.  It was originally started in 2004 by a local group in Bryan-College Station, Texas , led by David Bereit .  The name refers to a pattern of several events lasting for 40 days repeated in the Bible , such as in Noah's Ark , Moses's 40 days on Mount Sinai , and Jesus 's 40 days in the desert .
The campaign is active in the fall and spring of each year, though local campaigns may continue it throughout the year. The fall 2010 campaign launched in 238 locations around the world, including the United States , Canada , Australia , England , Northern Ireland , and Denmark .  The group reports that as of 2014, officially affiliated groups have been active in 25 countries.  The 2017 fall campaign is from September 27 until November 5.
The initial 2004 local campaign resulted in a rejuvenation of local pro-life activities in the Bryan-College Station area. Over the next two and a half years, the campaign was replicated in six other cities.  In early 2007, the leaders of those first campaigns got together and suggested a simultaneous nationwide 40 Days for Life campaign in as many cities as wished to participate. The first national campaign ran that fall with activities in more than 80 cities in more than 30 American states.  A second national campaign ran in the spring of 2008 during Lent , with events held in 59 cities.
The Spring 2009 campaign had numerous domestic and international cities participating, including Brisbane Australia, and cities in Canada, Northern Ireland, and the United States. During the Fall 2009 campaign, Abby Johnson , the director of the Planned Parenthood facility in Bryan, Texas (where 40 days for Life had originated), became a pro-life activist.  After holding a probe for an ultrasound guided abortion (Johnson was technically the facility manager and thus did not usually perform or assist in abortions) Johnson stated that she had seen "the baby move away from the probe".  Shortly after this experience, Johnson quit working for Planned Parenthood and joined the Coalition for Life, the local group that had been praying outside her former facility. 
The Fall 2010 campaign attracted attention when a Tennessee abortion provider was arrested for brandishing a handgun at three 40 Days for Life participants demonstrating outside a South Carolina abortion clinic.  After the spring 2013 campaign, the group says that the campaign involved over 100,000 participants from over 3,600 churches, in 253 locations across 10 countries, and that they are aware of 11,796 abortions stopped as a result of the campaign, and 73 clinics closed following the campaign. Campaigns continue to be held approximately semi-annually as of June 2016.
A 40 Days for Life campaign consists of 40 days of prayer and fasting   in shifts outside of a clinic or hospital that performs abortions, or which provides women having abortions elsewhere with advice, for 40 days.  Holly Baxter, a journalist for the British publication The Guardian states that the organization provides dubious health information during campaigns, and that presence of campaigns can be distressing to clinic patients, but finds that participants in the vigils are generally friendly.  The organization claims that its efforts have prevented 11,165 abortions globally since 2007.