The No. 1-ranked athlete in the 2016 class is a huge coup for the Tigers, who had signed five-star cornerback Kevin Toliver II in their 2015 recruiting class.
Smith, who took a weekend visit to Baton Rouge, chose LSU over Florida State, Florida, Clemson and Virginia Tech.
The 6-foot-1, 180-pound Smith projects as a defensive back at the next level, and he likely will begin his career as a cornerback.
After playing his freshman and sophomore seasons at Lakewood High in St. Petersburg, Florida, the 2016 Under Armour All-America Game selection transferred to IMG Academy and quickly became one of the school's top players.
He posted 67 tackles, five interceptions and three forced fumbles in 2014.
After signing the No. 10-ranked class in 2015, LSU looks poised to ink another highly ranked group with five ESPN Junior 300 players among the Tigers' seven early commitments. The Tigers have finished in the top 10 of the class rankings in each of the past three years, including No. 2 in 2014.
Along with Smith, the Tigers' class is headlined by another Sunshine State prospect: No. 32 overall and No. 4 pocket passer Feleipe' Franks. Other ESPN Junior 300-ranked players include No. 69 Stephen Sullivan, No. 227 Jamal Pettigrew and No. 286 Dee Anderson.
LSU remains in contention for other coveted prospects in the junior class, including No. 2 Shavar Manuel, No. 7 Edwin Alexander, No. 9 Keion Joyner, No. 15 Brandon Jones, No. 16 Rashard Lawrence, No. 22 Deontay Anderson, No. 24 Shyheim Carter (Alabama commit), No. 27 Edward Oliver, No. 29 Willie Allen and No. 31 Eric Monroe.