In terms of Olympic streaks, Phelps has ongoing runs of three straight golds in the 100-meter butterfly and the 200-meter individual medley. He will attempt to extend each of these streaks to four in a row. Before Phelps won the two aforementioned events in 2012, no male swimmer had won the same event at more than two straight Olympiad. He will swim a third individual event in Rio, namely the 200 butterfly, in which he narrowly missed a third straight gold in 2012.
The following chart (which you can click to enlarge) shows Phelps's medal performances not just at the past three Olympiad, but also at the World Championships and Pan-Pacific Championships. The chart includes only the three individual events he will swim in Rio. Phelps did not compete in 2013 due to his brief retirement, plus USA Swimming kept him off the team for the 2015 Worlds for his drunk-driving offenses.
Sports Illustrated's pre-Olympic issue picks Phelps to win one gold -- in the 100-meter butterfly, just ahead of Hungary's Laszlo Cseh. Within 2016, Cseh (50.86) has actually swum this race faster than Phelps (51.00), but we don't know that all circumstances (e.g., amount of rest; pool conditions) were comparable. (You can look up the world rankings in any event, based on fastest times, at the international federation's website.) SI tabs Cseh over Phelps in the 200 fly, and Japan's Kosuke Hagino over Phelps in the 200 IM.
