The Day of Cantabria Institutions, also known as 'Día de las Instituciones', is a significant public holiday in the autonomous community of Cantabria, located on the north coast of Spain. The holiday occurs annually on July 28th and serves as a commemoration of the local Cantabrian history, heritage, and regional identity. It is a day where Cantabrians pay homage to their local institutions and what they represent to the people of Cantabria.

The holiday holds deep historical significance as it celebrates the creation of the Province of Cantabria in 1778. The event took place in Puente San Miguel, Reocín, where the first autonomous assembly was held, marking a significant milestone towards Cantabria's quest for autonomy. This notable shift helped steer Cantabria into becoming the thriving region it is today. Citizens use this day to acknowledge the advancements made, recognizing the critical role of institutions in driving growth and development.

On the Day of Cantabria Institutions, numerous festivities occur throughout the region. The celebration includes cultural events, theatrical performances, and concerts. Various institutions and landmarks are opened to the public, offering locals and tourists the opportunity to learn more about Cantabria's rich history and vibrant culture. The sight of Cantabrian flags flying in pride and the spirit of togetherness on this day highlights the strong cultural cohesion in the region.