William Findlay Coolbaugh (July 1, 1821 – November 14, 1877) was an American politician and banker from Pennsylvania.

After working his way up the ranks at a Philadelphia dry goods house, he began his own store in Burlington, Iowa, in 1842.

He continued to learn the trade and was eventually tasked with all Western operations of the dry goods house.

Coolbaugh was the Democratic candidate for United States Senate in 1855, but was narrowly defeated by James Harlan.

In February 1865, the house was renamed the Union National Bank of Chicago; by 1867, it owned over $4.2 million in assets.

Coolbaugh died in Chicago on November 14, 1877, of an apparent suicide by gunshot in front of the Stephen A. Douglas Tomb.

Daughter Mary Ellen married Chief Justice of the United States Melville Fuller in 1866.