American golfer Shawn Stefani overcame a quadruple bogey on the 11th hole to seize a one-stroke lead after Saturday’s third round of the St Jude Classic.

Seeking his first US PGA title, he closed with three straight birdies for a four-under-par 66 to be one shot ahead of countryman Harris English, the 36-hole leader who could only manage a 69 on Saturday at TPC Southwind.

Stefani stands on 12-under 198 after 54 holes.

Four-time major champion Phil Mickelson fired a 65 and jumped to a share of sixth on 203, level with fellow American Eric Meierdierks and one behind compatriots Patrick Reed, Nicholas Thompson and Scott Stallings.

Ireland’s Padraig Harrington also fired a 65 to reach 204 and share eighth with Americans Ryan Palmer and Roberto Castro.

Stefani, whose best PGA showing was a share of seventh at last March’s Tampa Bay Championship in only his ninth PGA start, had back-to-back birdies at the second and third and again at the ninth and 10th.

Then came a quadruple-bogey at the par-3 11th that sent him tumbling down the scoreboard.

But Stefani answered with a birdie at the par-3 14th and then birdies on the final three holes.

English had a mild day by comparison, opening with a birdie and adding another at the par-5 third, then taking bogeys at the fifth and par-3 eighth before a birdie at 18 kept him one off the lead.

English also vying for his first PGA title at the $US5.7 million ($A6 million) event.

Meierdierks, who fired a 66, had a hole-in-one on the eighth.

Nick O’Hern was the best-placed Australian, eight shots off the lead on 206 after shooting a third-round 67.