"The River at Green Knowe" is a young adult novel written by L. M. Boston and first published in 1957. It details the summer holiday adventures of three young children, of which two are displaced, and the third is the great-niece of one of the women renting the house of Green Knowe.

As the summer in the country village of Penny Sokey rolls around, and the culinary aficionado Miss Sybilla Bun and archeologist Dr. Maud Biggin decide to rent the river island manor of Green Knowe. They decide to host two children from the Society for the Promotion of Summer Holidays for Displaced Children. Maud also sends for her great-niece, Ida, to come and visit to keep the children company.

The three children arrive soon after. Ida is eleven, small for her age, but very confidence. She has emerged as the leader of the trio of friends. Oskar, a Russian refugee, is tall, proud, and independent. Ping, of Chinese origin, is quiet, polite, and meek. The three children befriend one another quickly, and set off on many adventures. Along the way, they return a baby swan to its mother, discover an abandoned mansion, come upon a hermit, and discover a treelike giant named Terak and his mother.

The children also endeavor to help Dr. Biggin and her research into giant peoples, by bringing her a giant tooth, which she presents at the archeological society she is a member of. Unfortunately, the society believes the tooth is a fraud. The children then decide to keep helping, and bring Dr. Biggin to the local stop of a traveling circus to see Terak perform. However at the circus, Dr. Biggin believes Terak is merely a trick or a fabrication. The children are heartbroken in the end, wondering why adults never see the amazing things in front of them. Oskar remarks very sadly that adults are always looking to the past rather than seeing what they have here and now and the book ends with that bittersweet observation.