Every artist needs a muse. For Jimmy Webb, the prolific singer-songwriter behind such hits as “MacArthur Park,” “Wichita Lineman” and “Up, Up and Away,” that muse remains country legend Glen Campbell.

“It’s clearly one of the most important relationships in my life,” Webb, 66, said of his friendship with Campbell. “Hal David and Burt Bacharach discovered this 15-year-old girl named Dionne Warwick (and) she made their music immortal… That was how it was with Glen. He was my messenger to the masses.”

The son of a Baptist minister, Webb still remembers the first album he ever bought: Campbell’s 1961 folk single “Turn Around, Look at Me.”

“I got down on my knees by my bed, and said, ‘Dear God, let me learn to write a song even half as good as ‘Turn Around, Look at Me’ and please let me work with someone like Glen Campbell,” recalled Webb, who was a teenager in Elk City, Okla., at the time.

“Ten years later, I’m working with him,” Webb added. “In my mind, (that) settles any doubts that anyone might have about (the existence of) a divine being.”

In 1964, Webb and his family moved to Southern California, where he studied music at San Bernardino Valley College before embarking on a Los Angeles songwriter career.

After some early success penning songs for The Supremes and Johnny Rivers, Webb achieved his first big hit with 1967’s “Up, Up and Away,” recorded by The 5th Dimension. The carefree tune swept the Grammy Awards — snagging Webb a statuette for Song of the Year.

Webb’s work with The 5th Dimension — he penned all the songs on their 1967 follow-up album, “The Magic Garden” — coincided with his budding partnership with Campbell.

The first time the two met, Webb had been hired to do a commercial for General Motors. He arrived at the recording studio to discover Campbell already there, plucking his guitar.

“Of course I recognized him. I put my hand out and said, ‘Mr. Campbell, I’m Jimmy Webb,’ ” the songwriter recalled. “He looked up and said, ‘When are you going to get that hair cut?’ ”

Despite their obvious differences, the long-haired songwriter and the clean-cut country star soon became fast friends. Campbell recorded Webb’s “By the Time I Get to Phoenix” as the title track of his 1967 album, cementing the song’s status as a pop standard.

Campbell went on to record roughly 40 of Webb’s songs, including “Wichita Lineman,” “Galveston” and “Where’s the Playground Susie.”

Webb confessed he was a bit in awe of the country singer. “I was like the rest of the America. I was amazed by the musicianship and the fact he could sing virtually anything he put his mind to,” he said.

“We never were politically aligned. He was a bit farther to the right and I was a bit farther to the left,” he added. “(But) politics don’t have a great deal to do with music. Music is a language that transcends these petty concerns.”

Of course, Campbell hasn’t been Webb’s only collaborator over the years. The lengthy list includes Art Garfunkel, Thelma Houston, Linda Ronstadt and Carly Simon.

Academy Award-nominated actor Richard Harris had a hit with 1968’s “McArthur Park,” earning Webb a second Grammy. (Donna Summers found similar success with her 1978 disco cover.) And country heavyweights Johnny Cash, Waylon Jennings, Willie Nelson and Kris Kristofferson dominated the country charts in 1985 with Webb’s Grammywinning song “Highwayman.”

“I’ve been pretty well recorded and rarely disappointed ,” Webb said, noting that there’s one musician he’d like to add to the list. “My secret dream is that one day Paul McCartney will take one of my pretty little folk songs (and record it).”

No slouch in the studio himself, Webb has recorded roughly a dozen albums of original material, including 2007’s “Live and at Large” and 2010’s “Just Across the River.” The latter features appearances by the likes of Jackson Browne, Billy Joel and Lucinda Williams.

“I really culled together the most successful songs I’ve had in the country market for this album,” explained Webb, describing “Just Across the River” as half of a two-album set. “There were all these nice little moments that added up to a very good listening experience.”

The second half, due out in March 2013, finds Webb reuniting with Joe Cocker, Amy Grant and others. “The affections run deep between me and the artists I’ve worked with,” he said.

Although Webb may not have quite as high a profile as many of those performers, his Midwestern modesty prevents him from resenting the fact.

“I guess I don’t have a lot of self-image problems. That’s not one of the things my parents encumbered me with,” said Webb, who has been inducted into the Nashville Songwriters Hall of Fame and the National Academy of Popular Music’s Songwriter’s Hall of Fame. “I’m very happy to be a songwriter.”