A folding support includes a linkage mechanism having two crossed and hinged linkage rods, and two mirror-image support mechanisms. Each support mechanism includes an upright rod, a sliding sleeve, a connector, and two diagonal bracing mechanisms. The sliding sleeve is slidably received on the upright rod. Each diagonal bracing mechanism includes a diagonal bracing rod and a bottom frame rod. An upper end of the diagonal bracing rod is hinged with the sliding sleeve, and a lower end of the diagonal bracing rod is hinged with one end of the bottom frame rod. An opposite end of the bottom frame rod is hinged with the connector, and a lower end of one linkage rod is hinged with the connector. A folding chair including the above-mentioned folding support is also disclosed. The folding chair with such folding support is easy to fold and has good supporting effect.