The single was released by VPAL Classic, digital arm of VP Records.
Oh Jah Jah replaced Sister Nancy's resurgent 1982 hit single Bam Bam, which now holds second spot. Also in the top five are Do You Wanna by Shifta and Che'Nelle, Three Little Birds by Bob Marley and the Wailers and Matisyahu's One Day.
Oh Jah Jah is Murphy's second reggae number in 18 months. In the summer of 2013, he teamed with rapper Snoop Dogg on the song Red Light.
In an interview with the website www.voiceonline.co.uk, Murphy spoke about his love for reggae.
"My favourite [Jamaican artiste] right now is Chronixx. I also like Beenie Man and I like old stuff too. I like Garnet Silk and of course, I love Bob Marley," he said.
In 1993, Murphy collaborated with Grammy-winning deejay Shabba Ranks for the single, I Was A King. A video for that song was filmed in Portland.
Eddie Murphy, 53, was one of the hottest names in entertainment during the 1980s. He was the star attraction on Saturday Night Live, before branching out into hit movies like 48 Hrs, Trading Places and Beverly
That success continued in the 1990s, thanks to movies like Coming to America and Boomerang. Other Murphy hit films include Shrek and The Nutty Professor.