Until 1947, the law code of Hammurabi was thought to be the most ancient. But in that year, a new law came to light. This one was promulgated by a king named Lipit-Ishtar. His claim to fame was short-lived, however. In 1948, the curator of the Iraq Museum in Baghdad (Taha Baqir) announced the discovery of two tablets inscribed with an older law code. The obscure king's name was Bilalama. This king may have lived about 70 years before Lipit-Ishtar, but still his code of laws is not the oldest. That honor goes to a Sumerian King named Ur-Nammu who predates Hammurabi by about 300 years.

A tablet was found and translated in 1952, outlining his codes. The tablet containing Ur-Nammu's code of law consists of a prologue and seven laws. In the prologue, we read about Ur-Nammu as a divinely appointed king who established justice throughout the land. This code is of great importance to the study of biblical law, which it predates by about five centuries.

Ur-Nammu was the founder of the third dynasty of Ur. This dynasty lasted a century. He lived around 2050 BC and can be found on the Sumerian King List. The two most famous monuments of Ur-Nammu's reign are the great ziggurat (temple) at Ur and his stele, of which fragments remain.

Sources:

"History Begins at Sumer: Thirty-nine Firsts in Recorded History" by Sammuel Noah Kramer © 1956 pp. 51-52

Ur-Nammu on Encyclopedia.com