(Named after the Basque toponym for the city: Bilbo) is the urban public transport service of the city of Bilbao. The current service was established in 1988 as an initiative by the Bilbao City Council to unify and reorganize the city's transport, which until then had been managed by the company TUGBSA (Transportes Urbanos del Gran Bilbao S.A.). The history of its concessionaires reflects the evolution of the sector:

As of early 2026, the network features a fleet of 143 vehicles with an average age of just 4.90 years, distinguished by their solid red color and the municipal logo (the letter B) above the doors. The service is in an advanced stage of transitioning to zero emissions, focusing on electric and hybrid technology to cover its 45 lines (28 regular, 9 Auzolineak, and 8 night or Gautxori lines). Although the service scope is municipal, it maintains excellent intermodality with Bizkaibus, Metro Bilbao, Euskotren Trena, Bilbao Tram, and Cercanías Bilbao, even reaching neighborhoods in neighboring municipalities such as Ollargan (Arrigorriaga), Zubileta (Barakaldo), and Enekuri (Erandio). After overcoming the ridership crisis caused by the arrival of the Metro in 1995, Bilbobus reached a historic record in 2025 with nearly 30 million passengers, maintaining a citizen satisfaction rating of 8.07 points. Annually, its units travel over 6.3 million kilometers at an average speed of 14.7 km/h, establishing itself as the heart of urban mobility in the city.

Since its municipalization in 1988, Bilbobus has been the heir to a transport tradition dating back over 130 years in the city. Under different names, TCSA (and formerly TUGBSA) operated pioneering milestones in Spain, such as the first electric tram in 1896, the first trolleybuses in 1940, and the emblematic blue microbuses or "azulitos" in 1960. After the unification of the brand, Bilbobus held the exclusivity of urban transport until the inauguration of the Metro in 1995, at which point the service began to evolve to complement the high-capacity network. The management and identity of the service have passed through several key stages:

This measure was implemented to improve the safety of female users.

Currently, Bilbobus guarantees that 99.8% of the population resides within 300 meters of a stop. With over 100,000 daily trips, the majority profile of the user is female (70%), and the primary reason for travel is work-related (44%). Lines 77 and 56 are established as the most used, each exceeding 2 million annual passengers. The service holds a high citizen rating (7.32/10), with the Gautxori being the best-rated, and remains competitive as the City Council subsidizes 70% of its cost. In 2025, the service reached its peak, hitting a historic record of nearly 30 million travelers.

Currently, the network consists of 37 daytime lines, divided into 28 regular lines (identified by numbers) and 9 Auzolinea lines (identified by the letter A). Most main lines start staggered between 05:15 AM and 07:00 AM, with A8 being the last to start at 08:00 AM. Daytime service mostly ends between 10:00 PM and 11:00 PM. However, Line 30 is the latest to finish, extending its last trip until 11:40 PM.

The Bilbobus night service, known as Gautxori, ensures mobility in the city during weekend nights. It is one of the highest-rated services by citizens, achieving a score of 7.4/10 in satisfaction surveys. Its operations follow these schedules:

A fundamental feature of this service is that cash payments (single tickets) are not accepted; access must be made exclusively via the barik smart card. All Gautxori lines have their terminus or hub at Plaza Circular, facilitating connections between the city center and the neighborhoods.