She let another lead slip away in the second set, and her potent serve let her down. She double-faulted twice in the last tiebreaker, the second time to give a match point to Kerber, who coolly finished off Williams with a service winner.
Williams, a four-time Olympian at 32, won her only singles medal — a gold — in 2000.
"Hopefully, there's 2016," she said.
Federer, seeded No. 1, endured two rain delays and a shaky moment late in the first set to beat Denis Istomin of Uzbekistan 7-5, 6-3. The four-time Olympian has yet to win a singles medal.
Serving at 5-all in the first set, Federer faced three break points and erased them all. He then broke and was in control from there.
Federer and Wawrinka later lost to unseeded Jonathan Erlich and Andy Ram of Israel, 1-6, 7-6 (5), 6-3. Federer and Wawrinka won the gold in doubles in 2008.
Serena Williams worked under Wimbledon's roof during a brief midday shower, and the conditions clearly suited her. She whacked winners even from behind the baseline, and more than once spun on one foot after smacking a shot, mixing a little body English with plenty of brute force.
Williams hit a Wimbledon record 102 aces en route to her fifth title at the All England Club last month, and the shot remains a dominant force, especially on grass. She hit three consecutive aces against Zvonareva and lost only seven points in six service games.
In the second set, the crowd tried to coax a comeback from the Russian, who won the bronze in 2008. But when she began tossing her racket in frustration, cheers for her turned to jeers.
And fans applauded Williams' domination.
"We love you, Serena!" a spectator near the top of the stadium shouted during the final changeover. Williams continued to stare sternly, but she wore a grin moments later as she walked off the court in triumph, waving to the stands dotted with U.S. flags.
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