Szent István-bazilika, also known as St. Stephen's Cathedral Basilica, is a Catholic temple in Budapest, Hungary's capital city, that is dedicated to St. Stephen I of Hungary. It serves as the co-cathedral for the Strigonia-Budapest Archdiocese.

The basilica, which serves as Budapest's cathedral, was given the designation of "minor basilica" by Pope Pius XI in 1931.

With a capacity for 8,500 people, it is the second largest religious structure in the nation and, along with the Budapest Parliament, one of the two highest structures in the city (standing 96 metres tall).

Around 1851, work on the project began; it was finished 54 years later, in 1905, and dedicated the following year. Construction was delayed because the dome needed to be repaired after being destroyed in 1868. The principal architect was Miklós Ybl, a Hungarian.

A three-story foundation, nearly the same size as the church itself, had to be constructed beneath the substantial structure, whose main façade faces the neighbouring Danube River.

It was 87 m long and 55 m wide when it was completed, and it was constructed in the Neoclassical style. Twin bell towers on either side of the main façade finish it. The right tower is home to Hungary's largest and heaviest bell, which weighs nine tonnes; the former bell, which weighed eight tonnes, was melted down during World War II.

Excellent panoramic views of Budapest may be enjoyed from the dome; it has 364 stairs or lift access to the top.

St. Destra, the mummified hand of Monarch Stephen I, the first king of Hungary and a saint, is the most significant relic of Hungarian Christianity and is kept in the chapel beyond the apse.

The basilica's interior is lavishly decorated with paintings, panels made of marble and jasper, reliefs, and sculptures that date from the 19th and 20th centuries. The statues by Alajos Stróbl and the picture by Gyula Benczr, "St. Stephen Asks the Virgin Mary for the Protection of the Country," stand out among the artwork.

Organ concerts can be heard inside the church due to its acoustics.