Burial at sea is the disposal of human remains in the ocean, normally from a ship, boat or aircraft. It is regularly performed by navies, and is done by private citizens in many countries. Burial-at-sea services are conducted at many different locations and with many different customs, either by ship or by aircraft. Usually, either the captain of the ship or aircraft or a religious representative (of the deceased's religion or the state religion) performs the ceremony.

The ceremony may include burial in a casket, burial sewn in sailcloth, burial in an urn, or scattering of the cremated remains from a ship. Burial at sea by aircraft is only done with cremated remains. Other types of burial at sea include the mixing of the ashes with concrete and dropping the concrete block to form an artificial reef such as the Atlantis Reef. Below is a list of religions that allow burial at sea, with some details of the burial.

In Christianity, the practice is accepted. It has specific liturgies for burial at sea.

Officially, the Roman Catholic Church prefers casket burials over cremations, but does allow for burials at sea of whole or cremated remains. The Church defines burial at sea as sinking remains in a worthy container to the sea bottom and final resting place. Burial at sea in a casket or in an urn is acceptable and not prohibited, but viewed as not preferable and should not be commonplace. Cremated remains are subject to the condition that the ashes are entombed in a mausoleum urn niche, columbarium, or buried on land or sea. Catholics believe it is not proper to scatter or pour the cremated remains over the sea, water, or on the land. According to the Roman Catholic Church this action does not give due respect to the remains of the deceased, nor does it allow for the closure, healing of family and friends, and prayers for the deceased. Likewise they see that the custom of housing the remains with family or friends and not placing the deceased in the ground does not offer loved ones a specific and sacred place to visit the deceased's remains. Visiting the deceased in a holy place provides believers with a space to offer prayers, commune with those who have gone before them in faith, and reminds them to await the resurrection of their own bodies. For burials at sea, the committal prayer number 406§4 is used in the funeral liturgy.

At Orthodox funerals, there is normally an open casket at the ceremony. At the grave site, there is a short prayer, after which attendants move to place flowers on the casket. A memorial service is typically held on the Sunday closest to the 40th day after death. Cremation is not approved, as bodies are sought to be preserved in burial as much as is feasible, for preparation of the general resurrection of the dead at the Second Advent.

The Anglican Communion allows for burial at sea. Historically, the body has to be sewn in canvas, and suitably weighted. Today, it is more common for the body to be placed in a body bag or, if coming from ashore, a coffin. The ship is then stopped and a short religious ceremony is performed. Typically, Protestant funeral rites usually include some form of Bible reading, prayers, a sermon and/or hymns. Exact practices vary by denomination. However, some Protestants do not pray for the dead at all as they state that God has already received the deceased.

At the burial of the dead at sea, the same office from the Book of Common Prayer as used for burial on land may be used; only instead of the words:

We therefore commit [his] body to the ground, earth to earth, ... in sure and certain hope of the resurrection of the body