Nikolaj Frederik Severin Grundtvig (Danish pronunciation: [ˈnekolaɪ̯ˀ ˈfʁæːˀðʁæk ˈsɛvəʁin ˈkʁɔntvi]; 8 September 1783 – 2 September 1872), most often referred to as N. F. S. Grundtvig, was a Danish pastor, author, poet, philosopher, historian, teacher and politician. He was one of the most influential people in Danish history, as his philosophy gave rise to a new form of nationalism in the last half of the 19th century. It was steeped in the national literature and supported by deep spirituality.

Grundtvig holds a unique position in the cultural history of his country. Grundtvig and his followers are credited with being very influential in the formulation of modern Danish national consciousness. He was active during the Danish Golden Age, but his style of writing and fields of reference are not immediately accessible to a foreigner, thus his international importance does not match that of his contemporaries Hans Christian Andersen and Søren Kierkegaard.