St. Willehad, Groß Grönau, Lutheran church in Groß Grönau, Germany.

St. Willehad is a single-nave brick church built in the mid-13th century. Its box-shaped choir, dated to the early Gothic period shortly before 1230, has a ribbed vault painted with squares and diamonds, corner pilasters, a frieze and a gable with blind patterns and an eastern group of three windows. The three-bay nave has four sturdy buttresses, and a half-timbered west tower with an octagonal spire was added between 1698 and 1705.

Groß Grönau appears as "Gronowe" in the Ratzeburg tithe register of 1230, when it still belonged to the Krummesse parish; soon after it became an independent parish. The brick church was built in the mid-13th century, its box-shaped choir dated to the early Gothic period shortly before 1230. The nave's cross vault collapsed on the night of 18 June 1737, after which the outer walls were raised and a flat wooden ceiling installed.

The church takes its name from Willehad, the 8th-century missionary who became Bremen's first bishop in 788. The east south window beside the pulpit holds eight coats of arms and house marks of former owners of Gut Tüschenbek, dated 1607, 1608 and 1664, topped by the guild emblem of the Stecknitz boatmen. The west north window was donated on Ewigkeitssonntag 1955 in memory of war dead, showing the arms of East and West Prussia, Pomerania, Lauenburg and Lübeck.

The church stands on a flat site in Groß Grönau, south of Lübeck, with the west tower facing the street; the choir with its three-window east group lies at the far end. The south portal of the choir opens through a newer porch. The nave's flat wooden ceiling and the 1934 refitting are visible inside; the 17 consecration crosses rediscovered that year remain on the walls.

During the 1934 restoration, 17 consecration crosses were rediscovered and restored; the original number was probably 18, with twelve in the nave and six in the chancel. The oldest, likely Gothic, layer of the cross on the eastern chancel wall differs from today's version in form and colour.