Robert Conrad, a rugged, contentious actor who starred in the hugely popular 1960s series “Hawaiian Eye” and “The Wild Wild West,” died Feb. 8 in Malibu, Calif. He was 84.

The cause was heart failure, said family spokesman Jeff Ballard.

With his good looks and strong physique, Mr. Conrad was a rising young actor when he was chosen for the lead in “Hawaiian Eye.” He became an overnight star after the show debuted on ABC in 1959, with Mr. Conrad playing Tom Lopaka, a daring private investigator whose partner was Tracy Steele (Anthony Eisley). They operated out of a fancy office overlooking the pool at a popular Waikiki hotel.

The two private eyes alternated on simple investigations with help from the island’s colorful characters, including a singer named Cricket Blake (Connie Stevens) and a ukulele-strumming taxi driver named Kazuo (Poncie Ponce).

After five seasons with the show, Mr. Conrad went on to embrace the television craze of the time, period Westerns, but with a decidedly different twist. In “The Wild Wild West,” which premiered in 1965, he was James T. West, a James Bond-like agent who used innovative tactics and futuristic gadgets (futuristic for the 1800s anyway) to battle bizarre villains. He was ably assisted by Ross Martin’s Artemus Gordon, a master of disguise.

The show aired until 1969 and inspired a 1999 movie of the same name, a box-office bomb starring Will Smith as West.

In 1976 came the series “Baa Baa Black Sheep,” roughly based on an autobiography by Marine Corps ace and Medal of Honor recipient Gregory “Pappy” Boyington, who wrote of the raucous fliers he commanded during World War II. Mr. Conrad played Pappy Boyington, so nicknamed because he often rescued his pilots from severe punishment. Bringing his customary intensity to the role, Mr. Conrad even learned to fly.

The NBC series was dropped after its first season and revived in December 1977 as “Black Sheep Squadron,” after the network’s new shows failed to find audiences. It continued for another season.

Mr. Conrad, meanwhile, interspersed his long, successful TV career with numerous roles in films. After a couple of small parts, his TV fame elevated him to stardom, starting in 1965 with “Young Dillinger,” in which he played Pretty Boy Floyd. Other films included “The Bandits” (1967), which he also directed); “Murph the Surf” (1975); “The Lady in Red” (1979, this time as John Dillinger); and “Wrong Is Right” (1982).

At the same time, he found plenty of time for arguments.

Throughout Hollywood, Mr. Conrad had a reputation as a tough customer and was sued more than a half-dozen times as a result of fistfights. Playing himself in a 1999 episode of the TV series “Just Shoot Me,” he lampooned his threatening, tough-guy persona. He was also featured in 1970s commercials for Eveready batteries, with a battery on his shoulder, a menacing stare and a popular catchphrase, “I dare you to knock this off.”

“I’m only about 5-feet-8 and only weigh 165 pounds as of this morning, so I’m not the world’s meanest guy,” he told an interviewer in 2008. “If you treat me nicely, I’ll treat you nicer,” he added. “If you’re rude to me, put your headgear on. Here it comes.”

His daughter Nancy Conrad, who appeared in some of his pictures, explained it this way: “Dad is a hard worker. If people drag their feet, he gets impatient. He starts ranting and raving. It takes a while to patiently take him aside and show him why things might not be going well.”

He frequently employed his children in his movies and TV shows.

An example was the 1988 television series “High Mountain Rangers,” which Mr. Conrad had proposed, bankrolled with his own money and directed. He hired sons Shane and Christian as co-stars, daughter Joan as producer and daughter Nancy as caterer. His first wife handled financial matters.

The show, about a group of law enforcement officers, was filmed in the High Sierra mountain range near Lake Tahoe.

Mr. Conrad’s later film credits included “Jingle All The Way” (1996) with Arnold Schwarzenegger and “Dead Above Ground” (2002).

He was born Konrad Robert Falkowski in Chicago on March 1, 1935. His great-grandfather had emigrated from Germany, and his grandfather founded several meat shops in Chicago called Hartman’s.

Mr. Conrad moved from one school to another, and at 15 he left his parents’ house for a place known only to his girlfriend and his great-grandmother, who sometimes fed him.

A football player in school, Mr. Conrad’s first job was loading trucks. Then at 18 he was hired to drive milk wagons. He tried boxing and nightclub singing for a time before drifting into acting and eventually moving to Hollywood, where he found work as a stuntman.

His marriages to Joan Kenlay and LaVelda Fann ended in divorce. Survivors include five children from his first marriage; three from his second; and 18 grandchildren.