| Named By: | Gregory S. Paul in 1988 |
| Time Period: | Late Jurassic, 150-145 Ma |
| Location: | Africa, Tanzania - Tendaguru Formation |
| Size: | Approximately 26 meters long |
| Diet: | unavailable |
| Fossil(s): | Several partial skeletons |
| Classification: | | Chordata | Reptilia | Dinosauria | Saurischia | Sauropodomorpha | Sauropoda | Titanosauriformes | Brachiosauridae | |
Giraffatitan, meaning "giant giraffe", is a genus of sauropod dinosaur that lived during the late Jurassic Period (Kimmeridgian-Tithonian stages). It was originally named as an African species of Brachiosaurus (B. brancai) but this has since been changed. Giraffatitan was for many decades known as the largest dinosaur but recent discoveries of several larger dinosaurs prove otherwise: giant titanosaurians (Argentinosaurus, Puertasaurus and Futalognkosaurus) appear to have surpassed Giraffatitan in terms of sheer mass. Also the sauropod dinosaur Sauroposeidon is estimated to be taller and possibly heavier than Giraffatitan.
All size estimates for Giraffatitan are based on the specimen HMN SII a subadult individual between 21.8-22.5 metres (72-74 ft) in length and about 12 meters (39 ft) tall. Mass estimates are varied from as little as 15 tonnes (17 short tons) to as much as 78.3 tonnes (86.3 short tons) but there is evidence supporting that these animals could grow larger HMN XV2, represented by a fibula 13% larger than the corresponding material on HMN SII which might have attained 26 metres (85 ft) in length or longer.