Rainbow Valley (1919) is the seventh book in the chronology of the Anne of Green Gables series by Lucy Maud Montgomery, although it was the fifth book published. In this book Anne Shirley is married with six children, but the book focuses more on her new neighbor, the new Presbyterian minister John Meredith, as well as the interactions between Anne's and John Meredith's children.

The book is dedicated: "To the memory of Goldwin Lapp, Robert Brookes and Morley Shier who made the supreme sacrifice that the happy valleys of their home land might be kept sacred from the ravage of the invader." This refers to World War I, which is the main theme of the next and final book in the series, Rilla of Ingleside.

Anne Shirley has now been married to Gilbert Blythe for 15 years, and the couple have six children: Jem, Walter, Nan, Di, Shirley, and Rilla.

After a holiday in Europe, Anne returns to the news that a new minister has arrived in Glen St. Mary. John Meredith is a widower with four young children: Gerald (Jerry), Faith, Una, and Thomas Carlyle (Carl). The children have not been properly brought up since the death of their mother, with only their absent-minded father (who is easily absorbed by matters of theology) and their old, bitter, and partially deaf Aunt Martha to take care of them. The children are considered wild and mischievous by many of the families in the village (who tend only to hear about the Meredith children when they have gotten into some kind of scrape), causing them to question Mr. Meredith's parenting skills and his suitability as a minister.

For most of the book, only the Blythes know of the Meredith children's loyalty and kindness. They rescue an orphaned girl, Mary Vance, from starvation, and Una finds a home for her with Mrs. Marshall Elliot. When the children get into trouble, Faith sometimes tries to explain their behavior to the townsfolk, which generally causes an even bigger scandal.

The Merediths, Blythes, and Mary Vance often play in a hollow called Rainbow Valley, which becomes a gathering place for the children in the book. Jem Blythe tries to help the Merediths behave better by forming the "Good-Conduct Club," in which the Merediths punish themselves for misdeeds. Their self-imposed punishments lead to Carl becoming very ill with pneumonia after spending hours in a graveyard on a wet night, and to Una fainting in church after fasting all day. When this happens, John Meredith is wracked with guilt over his failings as a father.

Mr. Meredith realizes that he should marry again and give the children a mother, though he has always thought he will never love anyone again as he did his late wife. He is surprised to find that he has fallen in love with Rosemary West, a woman in her late thirties who lives with her sister Ellen, who is ten years older. John proposes marriage to Rosemary, but Ellen forbids Rosemary to accept, as years earlier they had promised each other never to leave the other following the deaths of their parents. However, Ellen eventually reunites with her childhood beau, Norman Douglas, and asks Rosemary to release her from her promise so she can marry Norman. Rosemary agrees, but now thinks that John Meredith hates her.

Una overhears her father expressing feelings for Rosemary and goes to ask Rosemary to marry her father despite her misgivings about stepmothers, who Mary Vance has told her are always mean. Rosemary sets her mind at ease and agrees to speak to John Meredith again. They become engaged, and Rosemary and Ellen plan a double wedding in the fall.