Saudi Arabia Accountability and Yemen Act of 2018 This bill suspends certain weapons transfers to Saudi Arabia. It also imposes sanctions on individuals for various activities related to the civil war in Yemen and for involvement in the death of Saudi Arabian journalist Jamal Khashoggi. The United States may not authorize transfers to Saudi Arabia of missiles, ammunition, ground vehicles, aircraft, or other weapons that fall within Categories III, IV, VII, or VIII of the U.S. Munitions List. The prohibitions do not apply to ground-based missile defense systems and shall expire September 30, 2020. The United States may not provide in-flight refueling for Saudi coalition aircraft involved in the civil war. (A Saudi-led coalition has been fighting against Ansar Allah, a group in armed conflict with the government of Yemen.) The United States shall impose sanctions on individuals who are blocking the flow of humanitarian goods and services into Yemen or working to undermine the country's stability. This includes sanctions on supporters of Ansar Allah if the United States determines the group has not made meaningful efforts towards peace. This bill amends the Global Magnitsky Human Rights Accountability Act to impose sanctions on foreign individuals, including any members of the Saudi royal family, who are responsible for or who aided in Khashoggi's death.