Final answer:
In the modern world, Iran and Iraq are two nations with a significant Shi'i population.
Step-by-step explanation:
In the modern world, there are several nations that have a Shi'i majority or a significant Shi'i population. Two examples of modern nations with a significant Shi'i population are Iran and Iraq.
In Iran, Shi'i Islam is the official state religion, and the majority of Iranians are Shi'i Muslims. Shi'ism originated in Iran and is deeply rooted in its history and culture. The country has many important Shi'i religious sites, including the holy city of Mashhad and the shrine of Imam Reza.
In Iraq, the Arab population is predominantly Shi'i. The cities of Karbala and Najaf in Iraq are significant as holy sites for Shi'i Muslims worldwide. Karbala is the burial place of Imam Husayn, the grandson of the Prophet Muhammad, and Najaf is the burial place of Imam Ali, the cousin and son-in-law of the Prophet Muhammad.