The Hammer and the Cross is a science fiction novel by Harry Harrison and John Holm, a pseudonym for the Tolkien scholar Tom Shippey.

In this tale, the authors explore what might have happened if the Vikings had fought more successfully against the rule of Chalcedonian Christianity.

When he is not busy with mundane tasks, Shef finds himself aiding the village blacksmith, where he develops his talents as well as an affinity for invention.

A review in Runepebble called it "an interesting alternate history" and recommended it for older children as it was "violent but not without cause.

The reviewer described the book as "Fascinating[ly] sinewy, brutal, and fine—and never mind the sometimes wobbly plot and rather thin characters: few historicals are as powerfully evocative of time and place as Harrison's tremendous saga.