The Ramsay family are spending the summer in their holiday house on the Isle of Skye. Mr. Ramsay, a mathematician, and his wife, who runs the home, have eight children, including the beautiful Prue, who is likely to be married soon, and James, the youngest, still fiercely attached to his mother. There are also assorted guests, including Charles Tansley, one of Mr. Ramsay's students; Lily Briscoe, a keenly observant painter; and Mr. Carmichael, an opium-addicted poet.

James wants to be taken by boat to visit the lighthouse and his mother encourages him, but his father, enraging James, says it'll be impossible because of the weather. That night Mrs. Ramsay gives a dinner party where she orchestrates the complex dynamics of the family and their guests into a perfect social unit, which is presented as a kind of work of art.

This is followed by a short interlude, "Time Passes," which marks a shift in scale from the human to a wider view, where encroaching darkness and dissolution threaten the house and the lives connected to it. During this period, Mrs. Ramsay dies, Prue marries and then dies in childbirth, and a War takes place in which Andrew, another son, is killed.

All these events are diminished by the universal context of time and change against which Woolf places them. The final part of the novel returns to the human scale. About ten years later, the surviving characters are back at the house and Mrs. Ramsay, though dead, continues to be the central figure, motivating much of what occurs. Mr. Ramsay now takes the still-angry James to the lighthouse, and Lily Briscoe, inspired by her memory of Mrs. Ramsay, is at last able to complete the painting she began years before.