Sergeant Major Shelby S. Smith was born in Stockbridge, Georgia.  He entered recruit training on 04 December 2000.  In March 2001, he was meritoriously promoted to the rank of Lance Corporal and graduated from Mike Company, 3d Battalion, MCRD Parris Island, South Carolina. Following graduation from Marine Combat Training, Lance Corporal Smith attended Aviation Structural Mechanic Course, A1 School in NAS Pensacola, Florida and Fixed Wing Aviation Safety Equipment Mechanic School in NAS Oceana, Virginia where he was assigned military occupational specialty 6287.

In August 2001, Lance Corporal Smith reported to Marine All-Weather Fighter Attack Squadron 225 at MCAS Miramar, California, where he served as an Aviation Safety Equipment Mechanic. In March 2002, he deployed to MCAS Iwakuni, Japan attached to Marine Aircraft Group 12.  While deployed, he was promoted to the rank of Corporal in September 2002. Corporal Smith returned to MCAS Miramar in September 2002.

In February 2003, Corporal Smith deployed to Al Jaber AFB, Kuwait in support of Operation Southern Watch/Operation Iraqi Freedom.  He then attended Weapons Tactical Instructor Course at MCAS Yuma, Arizona in September 2003 as an Aviation Safety Equipment Work Center NCOIC.   From March to September 2004, he again deployed to MCAS Iwakuni, Japan.  In April 2004, he was promoted to the rank of Sergeant.

Sergeant Smith attended Top Gun Instructor Course at NAS Fallon, Nevada in November 2004 as an Aviation Safety Equipment Collateral Duty/Quality Assurance Representative.  In May 2005, Sergeant Smith transitioned to the Quality Assurance Division.  During this time, Sergeant Smith completed a third deployment to MCAS Iwakuni, Japan from August 2005 to March 2006.  In June 2007, he was promoted to Staff Sergeant.  From August 2007 to March 2008, Staff Sergeant Smith deployed to Al Asad Air Base, Iraq in support of Operation Iraqi Freedom.

Upon return, Staff Sergeant Smith received orders to recruiting duty and served as a canvassing recruiter, Assistant NCOIC and Detachment Commander for Recruiting Station Saint Louis, Missouri from September 2008 to August 2011. 

In September 2011, Staff Sergeant Smith reported to Marine All Weather Fighter Attack Squadron 224 at MCAS Beaufort, South Carolina.  In December 2011, he was promoted to the rank of Gunnery Sergeant.  While at MCAS Beaufort, he served as a Collateral Duty/Quality Assurance Representative, Aviation Ground Safety Manager, the Aviation Safety Equipment Work Center Staff NCOIC, Aviation Life Support Division Chief, Quality Assurance Division Chief and Squadron Gunnery Sergeant. 
In May 2015, he was frocked to the rank of First Sergeant and reported to Marine Corps Communication-Electronics School, MCAGCC Twenty-nine Palms, California.  During this time, First Sergeant Smith served as Company First Sergeant with Bravo Company, Alpha Company, and Charlie Company.  He also served as the Senior Enlisted Advisor for Air Control Training Squadron. 

In May 2016, First Sergeant Smith transitioned to Suicide Charley Company, First Battalion, Seventh Marine Regiment.  He deployed as a member of SPMAGTF-CR-CC 17.2 and in support of Operation Resolute Support in Afghanistan with the Army's 82nd Airborne.

In July 2018, First Sergeant Smith was assigned to Force Company, 3d Reconnaissance Battalion, 3d Marine Division, III Marine Expeditionary Force.  In March 2019, First Sergeant Smith was promoted to the rank of Sergeant Major. 

In March 2019, Sergeant Major Smith was assigned to 3d Supply Battalion, 3d Marine Logistics Group.  During this time, Sergeant Major Smith served as the CLR-35 Regimental Sergeant Major prior to their deactivation.

In August 2020, Sergeant Major Smith transitioned to 3d Maintenance Battalion, 3d Marine Logistics Group where he currently serves as the Battalion Sergeant Major.
Sergeant Major Smith's personal awards include the Navy and Marine Corps Commendation Medal (3 gold stars in lieu of fourth award), the Navy and Marine Corps Achievement Medal (gold star in lieu of second award) and the Military Outstanding Volunteer Service Medal.