Athletic Club Femenino B is a Spanish women's association football team based in Bilbao, in the autonomous community of the Basque Country, Spain.

At the same time they introduced a women's reserve team (which had been established by Leioa the previous year)[1] with the aim of developing players for the senior side.

Athletic B, whose players are usually between 16 and 21 years of age, are also regular participants in the Copa Vasca, a regional tournament for lower-league teams, and have won the trophy six times.

[4] In common with all other teams fielded by the club, only players who meet their recruitment policy of having a connection to the 'greater Basque Country' are eligible to join.

[5] With the second tier re-organised in the early 2020s into two groups, then into just one, with a resultant uplift in the average standards (combined with general progress in the women's game in that period due to increasing investment and professionalisation), the teenagers of Athletic B began to find it difficult to remain competitive and it was no great surprise when they were finally relegated from the Primera Federación in 2023–24;[6] this would have caused Athletic C to have been demoted, but they were also among the bottom places in their Segunda Federación group and would have dropped down in any event.