McDuck Manor is the mansion home of Scrooge McDuck.
McDuck Manor is a luxurious mansion built in Duckburg by Scrooge McDuck in the 1930's. It went through several designs over the years, presumably after it was destroyed in various adventures (as it seems unlikely the old tightwad would have had it remodeled on a whim). Scrooge lives and sleeps in McDuck Manor, though he also has quarters in his main Money Bin to sleep in when he works late (which is actually rather frequent). The Manor contains many keepsakes of Scrooge's past and extremely inconsistent furnishing, from the ludicrously expensive to the cheapest trash. It is surrounded by an extremely large, partially unexplored park.
Behind the scenes
McDuck Manor first appeared alongside Scrooge himself in 1947 in Christmas on Bear Mountain by Carl Barks. Scrooge is first seen sitting in an armchair in his mansion's heavily decorated living room, looking through a window. Barks would reuse an ill-defined Manor as Scrooge's housing in several later stories and one-pagers, as would other Western writers. The Manor was not so prominent, however, that other writers did not assume Scrooge simply lived in his Money Bin.
Don Rosa, who dislikes the concept of Scrooge having a home outside his Bin, only used McDuck Manor in the twelfth and final chapter of The Life and Times of Scrooge McDuck, The Richest Duck in the World, taking place in 1947; Rosa had Scrooge state that he was going to sell the Manor shortly and live at the Bin full-time, though from an in-universe perspective it seems almost unavoidable that Scrooge must have changed his mind shortly.
In the DuckTales series, McDuck Manor is Scrooge's recurring home and is actually a more often-seen location that the Money Bin, presumably because Scrooge judged the Manor a better place to raise children than the Bin.