Colonel Charles Denby (June 16, 1830 – January 13, 1904) was a U.S. Union officer in the Civil War and diplomat. He was the father of Edwin C. Denby, a U.S. Representative from Michigan, and later Secretary of the Navy, and Charles Denby, Jr., a diplomat.

Denby was born in Mount Joy in Botetourt County, Virginia to Nathaniel Denby and Sarah Jane Harvey. Denby's maternal grandfather, Mathew Harvey, was a soldier in Lee's Legion during the American Revolution. Denby received his early education at the Tom Fox Academy, Hanover County, Virginia.

During his early youth, Denby's father, a Virginia ship-owner and interested in European trade, was appointed to a post at Marseille, France. His functions there were similar to those of a consul-general, but the post was then known as Naval Agent of the United States. On taking up his post, Nathaniel Denby took his son with him, where attended the College Royal at Marseille and became fluent in the French language. Denby later attended Georgetown College, Washington, D.C., and the Virginia Military Institute, from which he graduated with high honors in 1850.

After graduating, Denby went to Selma, Alabama, where he taught school for three years. In 1853, he removed to Evansville, Indiana, which remained his home until his death. Evansville was then a town of six thousand inhabitants, which, from its position on the Ohio River, at the terminus of the Wabash and Erie Canal, seemed destined to a great development. At Evansville, Denby devoted himself to the study of law and to newspaper work. He represented his county in the Indiana House of Representatives during the session of 1856–57. While in the legislature, Mr. Denby became acquainted with Martha Fitch, daughter of U.S. Senator Graham N. Fitch, of Indiana, and they were afterward married.

With the attack on Fort Sumter marking the outbreak of the American Civil War, Denby raised a company of volunteer soldiers and guarded the powder magazine near Evansville, Indiana. On September 12, 1861, Denby was commissioned as the Lieutenant Colonel (second-in-command) of the 42nd Indiana Volunteer Infantry Regiment and mustered in at that rank on October 10, 1861. On October 1, 1862, Indiana Governor Oliver P. Morton commissioned Denby as Colonel of the newly formed 80th Indiana Volunteer Infantry Regiment. Denby was not mustered in at his new rank until October 21, 1862, so he was still serving with the 42nd Indiana when it took part in the Battle of Perryville Kentucky on October 8, 1862. It was there that Denby was twice wounded and had his horse killed under him. Colonel Denby officially took command of the 80th Indiana on or before November 22, 1862. In a letter to the army dated January 12, 1863, Colonel Denby resigned his commission, stating:

I suffer habitually in riding with a very severe cramp in my left leg - walking affords no relief. The cramp is caused by an accident which happened many years ago and the side effects whereof were scarcely felt by me until after I entered the service. I have consulted various medical advisors who uniformly say there can be no remedy. I have therefore no recourse left but to return to a sedentary life.

His resignation was accepted effective January 17, 1863, and he left the army based on a surgeon's certificate of disability.

After the war, Denby was elected as a First Class Companion of the Indiana Commandery of the Military Order of the Loyal Legion of the United States.