His quest for seven gold medals in the 2012 London Olympics will follow a slightly easier path than his eight medal tour de force in Beijing, but his seven events, some with heats, then qualifiers and then medal races, still require him to get into the pool 17 separate times this Olympics.
Here is a look at his busiest days as he attempts to hit 21 career gold medals.
11:02 a.m. - Men's 4x200m Freestyle - Qualifier
7:47 p.m. - Men's 200m Butterfly - Final
8:47 p.m. - Men's 4x200m Freestyle - Final
This is undoubtedly Phelps' toughest Olympic day; three races, two of which are for medal placement. He will get a bit of a break with two of the three races being relays, but the heightened intensity of Gold Medal races could wear on him.
The Butterfly is one of Phelps' favorite events, and he is heavily favored to win the event. His odds for the 200m Butterfly are currently (-500).
11:14 a.m. - Men's 100m Butterfly - Heats
8:16 p.m. - Men's 200m Individual Medley - Final
8:51 p.m. Men's 100m Butterfly - Semifinals
The Individual Medley Final will likely see a reunion of Phelps and his fiercest competitor Ryan Lochte. Lochte beat Phelps by .16 seconds in the 200m Individual Medley at the FINA World Championships last year, and claimed the new world record in the event. This race will be one of the most heavily anticipated of the 2012 London Games.
11:49 a.m. - Men's 4x100m Medley Relay - Heats
7:38 p.m. - Men's 100m Butterfly - Final
Relative to the two prior listings, August 3rd may seem like a cakewalk, but Phelps will be coming off racing three times the previous day. The 100m Butterfly is a race Phelps has historically dominated, but there are no guarantees against world-class competition.