Thomas J. Lacy (c. 1806 – January 11, 1849) was a justice of the Arkansas Supreme Court, serving as one of the first three members of the court from 1836 to 1845.
Born in Rockingham County, North Carolina, Lacy was a graduate of Chapel Hill College, according to some sources, "graduating at the top of his class in 1825". He then read law under John Pope in Springfield, Kentucky. Pope was "an ally of Andrew Jackson who would later serve as territorial governor in Arkansas", an important connection for Lacy.
In 1832, President Jackson appointed Lacy to a seat on the Arkansas territorial court. Lacy served with Townsend Dickinson in the constitutional convention of 1836 and was elected one of the first judges of the state supreme court. In 1842, Lacy wrote a decision in a case that sparked political controversy, described as follows:
On the expiration of his first official term he was re-elected without opposition, but in 1845, was compelled, by failing health, to resign. In search of a more congenial climate, he went to New Orleans, where he died of cholera at the age of 43.