Dennis Cliff Smith Jr. (born November 25, 1997) is an American professional basketball player for the Detroit Pistons of the National Basketball Association (NBA). He attended NC State University for one season of college basketball and earned second-team all-conference honors in the Atlantic Coast Conference (ACC) as a freshman as well as ACC Freshman of the Year. After the season, Smith decided to forgo his remaining college eligibility and declared for the 2017 NBA draft. He was selected ninth overall by the Dallas Mavericks.
Smith was selected with the ninth overall pick in the 2017 NBA draft by the Dallas Mavericks. On July 5, 2017 he signed his rookie contract. While Smith would be out of action during the 2017 NBA Summer League in Orlando, he would return to action just in time for the event in Las Vegas. Under the six games he played with the Mavericks out in Las Vegas, Smith recorded 17.3 points, 4.8 rebounds, 4.2 assists, and 2.2 steals per game in under 25.9 minutes of action, which earned him All-Summer League first team honors.
On October 18, 2017, Smith made his debut in the Mavericks' season opener, a 117–111 loss to the Atlanta Hawks, where he scored 16 points and had 10 assists. On December 29, 2017, he recorded his first career triple-double with 21 points, 10 rebounds and 10 assists in a 128–120 win over the New Orleans Pelicans. He was 5 of 7 from 3-point range and 8 of 12 overall. At 20 years, 34 days, Smith became the sixth-youngest player in NBA history to have a triple-double, behind LaMelo Ball, Lonzo Ball, Markelle Fultz, Luka Dončić and LeBron James. On May 22, 2018, he was named to the NBA All-Rookie Second Team.
On January 31, 2019, Smith was traded to the New York Knicks along with DeAndre Jordan, Wesley Matthews and two future first round draft picks in exchange for Kristaps Porziņģis, Tim Hardaway Jr., Trey Burke and Courtney Lee. On April 9, Smith recorded 25 points and 5 assists in a 96–86 win against the Chicago Bulls.