In building construction, topping out is a builders' rite traditionally held when the last beam (or its equivalent) is placed atop a structure during its erection.

After topping out, numerous elements of construction remain, including interior finish and most mechanical, electrical, and plumbing systems.

The practice of "topping out" a new building can be traced to the ancient Scandinavian religious rite of placing a tree atop a new building to appease the tree-dwelling spirits displaced in its construction. Long an important component of timber frame building, it migrated initially to England and Northern Europe, thence to the Americas. 

A tree or leafy branch is placed on the topmost wood or iron beam, often with flags and streamers tied to it. A toast is usually made and sometimes workers are treated to a meal. In masonry construction the rite celebrates the bedding of the last block or brick.

In some cases a topping out event is held at an intermediate point, such as when the roof is dried in.

The practice remains common in the United Kingdom, Germany, Austria, Czech Republic, Slovakia, Poland, and the United States.