Dungy played for the Steelers from 1977-78 and was a coach with the team from 1981-88.
Other returning nominees include running back Jerome Bettis and linebacker Kevin Greene, both 2013 finalists, kicker Gary Anderson and coach Bill Cowher.
Tampa Bay linebacker Derrick Brooks, who also played under Dungy, is a candidate, too. So are former Raiders punter Ray Guy and former Falcons and Eagles defensive end Claude Humphrey as senior nominees.
Harrison spent 13 seasons with the Colts, making 1,102 receptions for 14,580 yards and 128 touchdowns. An eight-time Pro Bowl receiver, Harrison had four consecutive seasons with at least 100 catches. He teamed with Peyton Manning for nearly all of those catches and retired second in career receptions to Jerry Rice.
Brooks won the 2002 NFL title with Buccaneers and was a Pro Bowler in 11 of his 14 seasons.
The election will take place Feb. 1, the night before the Super Bowl. Between four and seven new members will be selected to the Hall of Fame and will be enshrined next August.
A nominated player or coach must have been out of the game for five consecutive seasons before he can be considered for the hall. A contributor may still be active in his pro football career.
The 2014 list has 89 players, 16 coaches and 21 contributors, including former NFL commissioner Paul Tagliabue and longtime team owners Bud Adams Jr., Jack Kent Cooke, Edward DeBartolo Jr., Jerry Jones, Robert Kraft and Art Modell.
Other players who are first-time candidates for induction are quarterback Trent Green; running backs Shaun Alexander and Warrick Dunn; offensive linemen Willie Anderson and Walter Jones; linebackers Tedy Bruschi, Willie McGinest and Zach Thomas; defensive backs Rodney Harrison, Sam Madison and Patrick Surtain; and coaches Jon Gruden and Mike Holmgren.