WDEF-TV (channel 12) is a television station in Chattanooga, Tennessee, United States, affiliated with CBS. Owned by Morris Multimedia, the station maintains studios on Broad Street in Chattanooga. Its transmitter is on Hampton Road in nearby Signal Mountain, along Walden Ridge.

WDEF-TV was the first television station to sign on in Chattanooga, debuting on April 25, 1954. It was built by a consortium of the owners of WDEF radio and two competing applicants for the channel, which merged to avoid a hearing. Originally a primary NBC affiliate, it switched to CBS in 1956 ahead of the arrival of a second local station. Popular WDEF radio personalities were seen on the new station, among them talk show host Drue Smith and Luther Masingill, whose career in Chattanooga broadcasting spanned more than 70 years.

In its first decades on air, WDEF-TV was the market leader, including after the 1964 acquisition of the WDEF stations by Roy H. Park. However, the station's ratings gradually declined due to disinvestment as competing stations invested in their news departments. After selling off the WDEF radio stations in 1996, Park Communications was acquired by Media General in 1997, but there was no change in WDEF's ratings fortunes under Media General or Morris, which purchased the station in 2006.

When the Federal Communications Commission (FCC) lifted its multi-year freeze on new television station applications in April 1952, Chattanooga was assigned two VHF television channels, 3 and 12, and several Chattanooga stations began considering filing for them. The FCC received applications for channel 12 from three firms. Southern Television, Inc., had connections to the movie theater industry. Chattanooga radio station WDEF, which had placed an order for television equipment in 1951, proposed a station twice as powerful as any then on the air. Tri-State Telecasting Corporation was a group of local residents who also offered stock in the firm to the public; among its stockholders were the owners of radio station WAGC.

The FCC designated the three applications for hearing in April 1953. With the process dragging on and Chattanooga still without a local TV station, negotiations began on merging the applications, which was first reported in late November. The merger was made official on December 11. It saw Tri-State and Southern withdraw their applications in favor of buying 27.5% each of the stock in the parent company of WDEF radio and television. On January 20, 1954, an FCC examiner issued an initial decision favoring the combined WDEF application. Construction began after the commission issued the construction permit on January 28.

WDEF-TV began broadcasting a test pattern on April 15, 1954, with program service beginning on April 25. It broadcast from a transmitter on Signal Mountain, with studios on the fourth floor of the Volunteer Life Building downtown. It was a primary affiliate of NBC, in keeping with WDEF radio, though as the only station in Chattanooga it also aired programs of CBS, ABC, and DuMont Television Network. Much of the station's staff came from Nebraska, having been hired by Harold "Hap" Anderson, who had started KOLN-TV there the year before; when KOLN-TV merged with that city's KFOR-TV, much of the staff became redundant, allowing many of them to follow Anderson to Chattanooga.

The new television station drew on personalities Chattanoogans already knew from WDEF radio. Among them were Luther Masingill, who had been on WDEF radio since its start in 1941 and hosted matinee movies; sportscaster Herschel Nation; and Drue Smith, public affairs director and interviewer. Smith hosted a talk show, Drue at Two. A local children's program, Chickarooney and Friends, aired on weekdays; other programs included a variety show, Jalopy. Also among the early programming was news coverage. The original program plans called for an evening newscast consisting of ten minutes of wire service copy and five minutes devoted to local news. Mort Lloyd was one of the original news anchors and the most popular in the city, remaining with the station through 1958.

In 1956, the FCC approved Chattanooga's second television station, WRGP-TV (now WRCB) on channel 3. Even though WDEF radio and television had been NBC affiliates, WDEF-TV opted at that time to become a primary CBS and secondary ABC affiliate. The station also invested in improved facilities, increasing its effective radiated power to 316,000 watts in December 1956 and buying the former Glass House restaurant at South Broad and 33rd streets to serve as the basis for a new studio complex in 1957. The station converted the former restaurant into offices and built a two-story addition to house radio and television studios, which was dedicated in December 1958. That same year, Chattanooga gained a third TV station and primary ABC affiliate: WTVC (channel 9), which moved in from Rome, Georgia.