First recorded by Neil Diamond (1966, first released 1967).
Hit versions by The Monkees (US #1/UK #1/CAN #1/AUS #1 1966), Neil Diamond (US #51/MOR #31 1971), Robert Wyatt (UK #29 1974).
Also recorded by The Fifth Estate (1967), Neil Diamond (re-recording 1979).
From the wiki: “‘I’m a Believer’ was composed by Neil Diamond who’d already recorded his own version before it was covered by The Monkees. Diamond’s original recording, produced by the songwriting team of Jeff Barry and Ellie Greenwich, was eventually released on his 1967 album Just for You.
“Diamond’s original recording was also released as a single in 1971, charting in the US and Australia. A revised recording, featuring additional lyrics, appeared on Diamond’s 1979 album September Morn. Diamond had also suggested the song to The Fifth Estate who did record ‘I’m a Believer’ as the 1967 follow-up to their hit single ‘Ding-Dong! The Witch Is Dead’, but it did not chart.
“‘I’m a Believer’ was the second single release for The Monkees. It hit the #1 spot on Billboard Hot 100 (and elsewhere worldwide) for the week ending December 31, 1966 and remained there for seven weeks, becoming not only the last #1 hit of 1966 but also the biggest-selling record for the whole of the next year, 1967. It is one of the fewer than forty all-time singles to have sold 10 million (or more) physical copies worldwide.