氢氧化镓化学式为Ga(OH)₃，是镓(III)的两性氢氧化物，白色胶状沉淀，不易溶于水，易溶于盐酸。溶于氢氧化钠生成[Ga(OH)₄]。Ga(OH)₃酸性略强于氢氧化铝Al(OH)₃，这也是元素次周期性的一个表现。Ga(OH)₃能溶于氨水，而Al(OH)₃不溶。Ga(OH)₃受热生成Ga₂O₃，低温生成α-Ga₂O₃，380℃成β-Ga₂O₃。在强酸性溶液中，镓以Ga形式存在；在强碱性溶液中以[Ga(OH)₄]形式存在。

Gallium hydroxide, Ga(OH)₃ is formed as a gel following the addition of ammonia to Ga salts. It is also found in nature as the rare mineral söhngeite which is reported to contain octahedrally coordinated gallium atoms Gallium hydroxide is amphoteric. In strongly acidic conditions, the gallium ion, Ga is formed. In strongly basic conditions, Ga(OH)₄ is formed. Salts of Ga(OH)₄ are sometimes called gallates.