lunette

thumb|upright=1.35|Lunette over the main door of the Luxembourg Palace in Paris thumb|Charles Sprague Pearce, Rest (1896). Mural in a lunette in the [[Thomas Jefferson Building of the Library of Congress, Washington, D.C.]]

A lunette () is a crescent- or half-moon–shaped or semicircular architectural space or feature, variously filled with sculpture, painted, glazed, filled with recessed masonry, or void. A lunette may also be segmental, and the arch may be an arc taken from an ellipse. A lunette window is commonly called a half-moon window, or a fanlight if its muntins (the bars separating its panes) diverge radially.