Iceberg B-9 was an iceberg that calved from Antarctica in 1987. It measured 154 kilometres (96 mi) long and 35 kilometres (22 mi) wide; it had a total area of 5,390 square kilometres (2,080 sq mi), and is one of the longest icebergs ever recorded. This calving took place immediately east of the future calving site of Iceberg B-15; it carried away Little America V which had been closed in December 1959. Starting in October 1987, Iceberg B-9 drifted for 22 months, covering 2,000 kilometres (1,200 mi) on its journey. Initially, B-9 moved northwest for seven months, before being drawn southward by a subsurface current that eventually led to its colliding with the Ross Ice Shelf in August 1988. It then made a 100-kilometre (62 mi) radius gyre before resuming its northwest drift. It moved at an average speed of 2.5 kilometres (1.6 mi) per day over the continental shelf, as measured by NOAA-10 and DMSP satellite positions, and by the ARGOS data buoy positions. In early August 1989, B-9 broke into three large pieces north of Cape Adare. These pieces were designated as B-9A, 56 by 35 kilometres, B-9B, 100 by 35 kilometres, and B-9C, 28 by 13 kilometres.

An iceberg is a piece of freshwater ice more than 15 m long that has broken off a glacier or an ice shelf and is floating freely in open water. Smaller chunks of floating glacially derived ice are called "growlers" or "bergy bits". Much of an iceberg is below the water's surface, which led to the expression "tip of the iceberg" to illustrate a small part of a larger unseen issue. Icebergs are considered a serious maritime hazard.