It accuses the Saudi-led coalition aiming to restore the exiled government of carrying out unlawful air strikes.
The Houthi rebel movement and its allies are meanwhile condemned for using heavy weapons indiscriminately.
On Tuesday, coalition warplanes targeted Houthi positions in the Red Sea port of Hudaydah, reportedly destroying cranes and warehouses at the aid hub.
There were also clashes overnight in the third city of Taiz, where the Houthis and allied army units loyal to former President Ali Abdullah Saleh have made advances.
The UN says that since the coalition began its bombing campaign on 26 March, at least 1,950 civilians have been killed and 4,271 wounded in air strikes and fighting.
Amnesty’s 30-page report documents eight air strikes that took place in June and July and resulted in the deaths of 141 people, mostly women and children.
The human rights group said the evidence gathered had revealed a pattern of raids targeting heavily-populated sites, including a mosque, a school and a market. In the majority of cases, no military target could be located nearby, it added.
Amnesty also investigated 30 attacks on the ground in the second city of Aden and in Taiz by the Houthis and anti-Houthi armed groups, which left 68 civilians dead.
Fighters from both parties routinely used imprecise weapons including Grad-type rockets, mortars and artillery fire in densely-populated residential areas, displaying utter disregard for the safety of civilians, the group found.
Amnesty called on the UN Human Rights Council to create an international commission of inquiry to independently and impartially investigate alleged war crimes in Yemen.
Northern Shia Muslim rebels known as Houthis, backed by forces loyal to Yemen’s ex-president, took over parts of Yemen, including Sanaa, and forced the government into exile in March
The rebels accused the government of corruption and of planning to marginalise their heartland within a proposed federal system
Forces loyal to the government, and southern militia, are fighting back, aided by air strikes led by neighbouring Saudi Arabia.