Atletico Madrid and Athletic Bilbao: Shared Origin, Split and Kits

Two clubs four hundred kilometres apart wear nearly the same shirt, and it is not a coincidence or a tribute. For the first eighteen years of its existence, Atletico Madrid was formally a part of Athletic Bilbao.

A Branch Office, Not a Club

The founding date is 26 April 1903, and the founding name says everything: Athletic Club Sucursal de Madrid. Sucursal means branch. Three Basque students living in the capital set it up as a youth offshoot of the club they had grown up with, giving Basques in Madrid somewhere to play under the name they already answered to.

Branch clubs of that era were not franchises in the modern sense, but they were not independent either. The Madrid side took the parent club’s name and the parent club’s colours, blue and white halved shirts of the kind Bilbao wore in 1903, and operated in the parent club’s shadow. Nothing about the arrangement anticipated that the branch would one day win eleven league championships of its own.

The Year the Club Stopped Being Basque Only

The first change came quickly and from an unexpected direction. In 1904 the club was joined by dissident members of Real Madrid, players and officials who had fallen out with the club across town and brought themselves over.

That single detail reframes the whole early history. The Madrid derby is usually told as a story of two separate institutions that grew to dislike each other; in fact the two clubs exchanged people in their first years, and Atletico’s transformation from a Basque students’ society into a Madrid club with a Madrid membership began with an influx from the club it would spend the next century measuring itself against. The derby page picks the rivalry up from there.

1911: The Shirts Change, and So Do the Shorts

Both clubs bought their kits from England, and both ordered the same thing: Blackburn Rovers’ blue and white. Then, at the turn of the 1910s, both changed to red and white stripes: Bilbao by 1910, Madrid in 1911.

Why they changed is genuinely disputed, and three accounts survive: a botched 1909 kit-buying trip that came back with fifty Southampton shirts, the cheapness of red-and-white mattress ticking, and a 2023 claim for Sunderland as the source instead. The full argument sets out all three and settles none of them.

What is not disputed is the detail that has kept the two clubs distinguishable ever since. When the stripes arrived, Madrid kept the blue shorts they had worn as a branch club. Bilbao moved to black. A hundred years later that is still the fastest way to tell the two kits apart, and it is the earliest surviving evidence of the Madrid club making a decision the parent club did not.

1921: Independence

Formal separation came in 1921, when Athletic Madrid became independent of Athletic Bilbao. Eighteen years after its founding, the branch became a club.

What followed shows how completely the two diverged. Bilbao built an identity around a recruitment policy that has no equivalent anywhere else in European football, signing only players from the Basque Country or developed in its clubs. Madrid went the other way entirely, with a merger with an air force club in 1939, three name changes between 1939 and 1947, and eventually a squad drawn from wherever the club could find players, which produced a nickname of its own when a wave of South American signings arrived and rival supporters started calling the team los indios. The nicknames page traces that.

What the Two Clubs Still Share

The shirts, obviously, and the origin. Beyond those, a small and specific thing: the phrase Athletic in the founding name, which Madrid carried until a 1940 decree banned foreign names and turned Athletic Aviacion de Madrid into Atletico Aviacion de Madrid. Bilbao kept theirs and still have it. The two clubs are, in that narrow sense, the same word in two languages.

There is also a competitive footnote. When Atletico said goodbye to their old ground on 21 May 2017, the opponents were Athletic Bilbao. The last league match at the Vicente Calderon ended 3–1 to the home side, with Fernando Torres scoring twice inside eleven minutes. Whether the fixture was chosen deliberately or fell that way in the calendar, the club that Atletico had once been a branch of was in the away end for the final act of a fifty-one-year home. The Vicente Calderon page covers that afternoon in full.

Was Atletico Madrid founded by Athletic Bilbao?

Effectively yes. The club was founded on 26 April 1903 as Athletic Club Sucursal de Madrid, the Madrid branch, by three Basque students who saw it as a youth offshoot of Athletic Bilbao. It remained formally attached to Bilbao until 1921.

When did Atletico Madrid become independent of Athletic Bilbao?

In 1921, eighteen years after its founding. The club had already begun changing character in 1904, when dissident members of Real Madrid joined.

Why do Atletico Madrid and Athletic Bilbao wear the same shirt?

Because Madrid began as Bilbao's branch club and wore the parent club's colours. Both switched from blue and white to red and white stripes at the turn of the 1910s, Bilbao by 1910 and Madrid in 1911, and neither changed back.

How can you tell the two kits apart?

By the shorts. When the stripes arrived, Madrid kept the blue shorts of their branch-club days and Bilbao moved to black. That difference has survived every kit redesign since.

Do the two clubs still have a formal relationship?

No. The separation in 1921 was complete, and the two have taken opposite paths since: Bilbao built an identity around signing only Basque-developed players, while Atletico recruited internationally, merged with an air force club in 1939 and changed its name three times before 1947.