Széchenyi lánchíd or Széchenyi Chain Bridge is a suspension bridge that spans the River Danube between Buda and Pest, the western and eastern sides of Budapest, the capital of Hungary. It was the first permanent bridge across the Danube in Budapest, and was opened in 1849.

Its two ends are:

* Roosevelt Square (with the Gresham Palace and the Hungarian Academy of Sciences), and
* Adam Clark Square (the Zero Kilometer Stone and the lower end of the Castle Hill Funicular, leading to Buda Castle).

The bridge is named after István Széchenyi, a major supporter of its construction. At the time of its construction, it counted as a wonder of the world. It had an enormous significance in the country's economics and life. Its decorations made of cast iron, and its construction, radiating calm dignity and balance, raised it among the most beautiful industrial monuments in Europe. It became a symbol of advancement, national awakening, and the linkage between East and West.

The bridge was designed by the English engineer William Tierney Clark in 1839, after Count István Széchenyi's initiative in the same year, with construction supervised locally by Scottish engineer Adam Clark (no relation). It is a larger scale version of William Tierney Clark's earlier Marlow Bridge, across the River Thames in Marlow, England.

The bridge was opened in 1849, and thus became the first permanent bridge in the Hungarian capital. At the time, its center span of 202 m was one of the largest in the world. The pairs of lions at each of the abutments were added in 1852. The bridge was given its current name in 1898.

The bridge's cast iron structure was totally updated and strengthened in 1914. In World War II, the bridge was damaged and needed to be rebuilt. The rebuilding was completed in 1949.

Among the mythical anecdotes relating to the bridge, the most popular is that the lions were sculpted without tongues and the sculptor was mocked so much that he jumped into the Danube in shame. The lions do have tongues (although they are not visible from below, which is the usual point of view, as the lions are lying on a stone block some three meters high). The sculptor lived into the 1890s, and the only message he sent to mocking people was "Your wife should have a tongue just as my lions have, and woe will be unto you!" He jumped into the Danube when a little boy asked him about it.[citation needed]

In 2001, Hungarian stunt pilot Péter Besenyei flew upside down under the bridge, a maneuver that became a standard in Red Bull air races today.

The bridge is featured in the 2002 movie I Spy.

In 2008, British crime writer Mark Van Spall (author of Heirless Descent and Prisoners of Hate) proposed to his girlfriend at the centre of the bridge on the stroke of midnight.