Robert "Rob" Marionneaux was born October 7, 1968, in Baton Rouge, Louisiana, to Patricia Smith Marionneaux and the late Robert M. Marionneaux, Sr. of Maringouin. He is married to Keely Williams Marionneaux and they have one son, Robert M. Marionneaux, III. Rob grew up on a small farm in rural, Maringouin, Louisiana.

Upon graduating from Catholic High of Pointe Coupee, Rob attended Louisiana State University in Baton Rouge, La, where he received his Bachelor of Science Degree in Criminal Justice, and a minor in psychology and sociology. While attending LSU, Rob was elected to serve as the Criminal Justice Representative on the General College Student Council. Thereafter he was elected president of The General College, LSU's largest college. On the social scene Rob was a member of Sigma Nu fraternity.

After completion of his studies at LSU Rob worked as an office manager for a small law firm before enrolling in Southern University Law Center where he was on the Dean's List and represented the Law Center in various capacities. Based on his academic performance Rob was invited to participate in Law Review. After participating in trial competition he and his teammates won awards for Best Brief & Best Oral Argument. He was also elected Vice President of the Law Center, Southern's first Caucasian student representative.

Upon graduating from Southern University Law Center, and while studying for the bar exam, Rob announced his candidacy for State Representative. At the age of 27 years, Rob was elected to the Louisiana House of Representatives representing the 18th district which comprised of parts of Iberville, Pointe Coupee, West Baton Rouge, and West Feliciana. While in the House Rob served on the Criminal Justice, Transportation and Agricultural committees.

After serving one term, Rob decided to run for State Senator. After a bitter campaign, one which drew the ere of the widely popular governor, Mike Foster, Rob emerged victorious. In the Louisiana Senate, Rob serves on Joint Capitol Outlay and Agriculture committees. He has been an outspoken voice for those unable to speak for themselves. Rob has never been afraid to be the lone vote in the Louisiana Senate on issues he feels are important. He also serves as a board member on the Mental Health Board of Louisiana.

Rob is a partner in the law firm Unglesby & Marionneaux which is located in Baton Rouge, Louisiana where he and his partner, Lewis Unglesby concentrate on personal injury, and criminal defense. He has represented thousands of individuals in their quest for justice.

His hobbies include hunting, fishing, snow skiing and working on his cattle farm located in Grosse Tete, Louisiana. Rob is a member of Immaculate Heart of Mary Catholic Church in Maringouin. He is a member of the Louisiana State Bar Association, the Louisiana Cattleman's Association, Louisiana Farm Bureau, Ducks Unlimited, and The National Wild Turkey Federation.