A Latin term meaning "against a thing." An in rem proceeding adjudicates the rights to a particular piece of property for every potential rights holder, even potential rights holders who are not named in the lawsuit. For example, a plaintiff may bring an in rem action to conclusively determine ownership rights over a parcel of land.

Generally, an in rem proceeding must be commenced in the jurisdiction where the subject property is located. The presence of the subject property in the forum state usually satisfies any due process concerns for binding out-of-state claimants to the court's judgment. However, notice of the suit still must be given to all individuals known to have interests therein.

A judgment in an in rem proceeding is limited to the property that supports the court's jurisdiction.