The Merman's Children is a 1979 fantasy novel by American writer Poul Anderson, inspired by legends of Mermen and Mermaids from Danish folklore, in particular the ballad Agnete og Havmanden.

Set at the end of the medieval era, The Merman's Children details the Faery peoples being displaced by the advancing tide of Christianity.

The city of Liri, ruled by King Vanimen, lies beneath the waves off the shores of Denmark and peacefully coexists with the landbound humans.

Vanimen was once married to a human woman, Agnete, until she returned to land; their four halfling children are Tauno, Eyjan, Kennin, and Yria.

Upon the exorcism, an earthquake destroys Liri, and a bright light and deafening sound force the merfolk to flee with only what they can carry.

Aiding them are Ingeborg, a prostitute who is in love with Tauno, and Niels, a young sailor who falls for Eyjan, but tensions with the rest of the crew are high.

Leaving Ingeborg and Niels in Denmark to discreetly sell off the treasure, Tauno and Eyjan set out to search for their people around Greenland.

They track the rumors to a Norse settler, Haakon Arnorsson, whose group is starving and trapped on land by a tupilak after they slaughtered an Inuit village.

The rumors of an underwater town turn out to be false, but Haakon holds Eyjan hostage to force Tauno to help kill the tupilak.

While he sleeps, Ingeborg takes the amulet and merges with Nada herself, giving up Christian salvation in order to become faery and spend an immortal life with Tauno.