Big Brother 2002, also known as Big Brother 3, was the third series of the British reality television series Big Brother. It is based upon the Netherlands series of the same name, which gained notoriety in 1999 and 2000. The series premiered on Channel 4 on 24 May 2002 and lasted nine weeks until the live finale on 26 July 2002. The third edition saw a ratings increase for the series. The finale had a total of 10 million viewers which is not only the most watched episode of Big Brother to date but, based on Live +7 data supplied by BARB, is Channel 4's most watched broadcast since the channel's inception in 1982. In total, over 8.6 million votes were cast to determine the winner of the series. In terms of average viewers, Big Brother 3 is the highest rated series of the show to date, averaging 5.9 million viewers throughout the whole season. It is one of only two seasons of the main series to have over five million average viewers. More than 150,000 viewers applied to be on this season, more than double the amount of applicants from the previous edition. Davina McCall returned as host.

This series saw a number of changes and a number of firsts which would continue in future series: it was the first series to be filmed at Elstree Studios, where it still operates as of 2013, interviews with the housemates took place inside the George Lucas Stage and remained here until Ultimate Big Brother in 2010. It was the first and only series to issue a 'three strikes and you're out' form of disciplinary, all succeeding series have simply issued formal warnings to a housemate who breaks the rules. Big Brother 3 also started the eviction process not being limited to housemate nominations, in Week 1, the public made the nominations and the housemates made the final decision on who would go, in Week 7, two housemates faced eviction simply for being given video messages from home, future series also began experimenting with the eviction process. The first eviction took place a week earlier than the previous two series', rather than wait two weeks to evict a housemate, the first eviction took place just one week after the housemates entered, evictions in the first week have since become common in subsequent seasons. It was the first non-celebrity series to feature a Live Launch Show - although the previous celebrity series featured one. Previously, 10 housemates would enter the house on Day 1, usually with one other housemate arriving later on in the series, Big Brother 3, saw the arrival of 12 housemates on launch night, two housemates left the house voluntarily - this was the first time this happened, but quitting has become more common over the years - both were replaced by standby contestants, making it the first time to feature more than one non-original housemate, again late entry housemates have become more common in subsequent series. Big Brother 3 saw the house divided into 'Rich/Poor' for four weeks, a live task broadcast on Saturday nights would determine which side the housemates would end up living for the week. The Rich/Poor divide was not used again until the ninth series in 2008, where it was renamed Heaven/Hell.