Brachiosauridae is a family of very large sauropods characterized by forelimbs longer than their hindlimbs, which gave them a distinctive steeply inclined, giraffe-like posture and let them browse foliage well above the reach of most other herbivorous dinosaurs. Their necks were exceptionally long and their nostrils sat atop a tall, arched skull, a feature that once led to speculation about aquatic habits, now generally rejected in favor of the nostrils serving a role in airflow or thermoregulation. Known from the Late Jurassic through the mid-Cretaceous, brachiosaurids lived roughly 154 to 100 million years ago and reached lengths of 18 to 21 meters or more.
The family's best-known member is Brachiosaurus itself, described from the Morrison Formation of North America, alongside close relatives such as Giraffatitan from the Tendaguru beds of Tanzania, long treated as a species of Brachiosaurus before being recognized as a distinct genus. Additional material attributed to the family has been found in Europe and possibly Africa and Asia, suggesting a broad distribution across Jurassic Laurasia and Gondwana before continental separation restricted later sauropod lineages to more regional ranges. Brachiosaurids are frequently used in popular reconstructions of Jurassic ecosystems because of their height and instantly recognizable silhouette.