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Abdul Aziz ibn Muhammad ibn Saud (Arabic: عبد العزيز بن محمد بن سعود ‎) was the second ruler of the First Saudi State and son of Muhammad bin Saud. He was also the son-in-law of Muhammad bin Abdul Wahhab. He ruled from 1765 until 1803.

During his reign, the grasp of the House of Saud extended into Riyadh with Abdul Aziz's victory there and subsequent conquest. This victory allowed the House of Saud to rule all of Nejd. Their military success and orthodox approach to religion won them great support in the area. Their standing was also boosted by Abdul Aziz's practice of holding open meetings where tribal elders could meet with him, allowing access to their ruler.

One notable event of his reign were demolition the sepulcher of Ali bin Abu Talib in Najaf, Iraq and on the sepulcher of Imam Husayn in Karbala, Iraq. This was done in 1802.

In 1803, Abdul Aziz ibn Saud was assassinated by a shia sectarian man from A'amarah in Iraq by a stiletto, when Abdul Aziz ibn Saud was leading the prayers of 'Asr salah in Dir'aiyah.