Nimitz Hill Annex is a community and census-designated place (CDP) in Asan-Maina, Guam. It contains the geographic feature of Nimitz Hill, and is located immediately northeast of the Nimitz Hill CDP in Piti. In normal conversation, the Nimitz Hill CDP and Nimitz Hill Annex CDP are often collectively referred to as "Nimitz Hill."

Asan-Maina is a village located on the western shore of the United States territory of Guam. The municipality combines the names of the coastal community of Asan with Maina, a community along the slopes of the Fonte River valley to the east. Asan was the northern landing site for United States Marines during Guam's liberation from the Japanese during World War II. Asan Beach Park is part of the War in the Pacific National Historic Park. The third community comprising Asan-Maina is Nimitz Hill Annex in the hills above Asan and Maina, which is the location of the Joint Region Marianas headquarters. Asan-Maina is located in the Luchan (Western) District.