A groomsman or usher is one of the male attendants to the bridegroom in a wedding ceremony. The term groomsman is more common in the United States, and usher is more common in the UK. Usually the bridegroom selects his closest friends and/or relatives to serve as a groomsmen, and it is considered an honor to be selected. From his groomsmen, the groom usually chooses one to serve as best man. The duties of the groomsmen are to help guests find their places before the ceremony and to participate in the wedding ceremony.

Additionally, the groom may request other kinds of assistance, such as planning celebratory events such as a bachelor party, also called Stag Night or Buck's Night; helping make the wedding pleasant for guests by talking with people who are alone or dancing with unpartnered guests or bridesmaids, if there is dancing at a wedding reception; or providing practical assistance with gifts, luggage, or unexpected complications. Groomsmen may also participate in local or regional traditions, such as decorating the newlywed couple's car.

For a wedding with many guests, the groom may also ask other male friends and relatives to act as ushers without otherwise participating in the wedding ceremony; their sole task is ushering guests to their seats before the ceremony. Ushers may also be hired for very large weddings.
In a military officer's wedding, the role of groomsmen is replaced by swordsmen of the sword honor guard. They are usually picked as close personal friends of the groom who have served with him. Their role includes forming the traditional saber arch for the married couple and guests to walk through.

Bridegroom-men and bridesmaids had formerly important duties. The men were called bride-knights, and represented a survival of the primitive days of marriage by capture, when a man called his friends in to assist to "lift" the bride.