Jon Santiago is an American physician and Democratic politician who served in the Massachusetts state representative for the 9th Suffolk district from 2019 to March 2023. He ran a campaign for mayor of Boston in 2021, but withdrew from the race before the primary election.

The Massachusetts House of Representatives is the lower house of the Massachusetts General Court, the state legislature of Massachusetts. It is composed of 160 members elected from 14 counties each divided into single-member electoral districts across the Commonwealth. The House of Representatives convenes at the Massachusetts State House in Boston, the state capital of Massachusetts.