E-M81 is a branch on the paternal tree of human kind. It and branches help trace human history from our origin in Africa.
This branch is defined by the Y-Haplotree at FamilyTreeDNA as E-M81. There, it is the child of the E-L19 branch.
M81, BY1996, BY2268, BY47661, BY48466, BY48604, BY8883, BY8885, CTS10196, CTS10321, CTS11147, CTS1294, CTS1819, CTS3350, CTS3415, CTS3870, CTS5819, CTS5883, CTS7132, CTS8527, CTS87, M183, M5023, M5094, M5300, M5303, M5358, M5364, PF1585, PF2326, PF2401, PF2485, PF2486, PF2489, PF2490, PF2491, PF2493, PF2494, PF2498, PF2499, PF2500, PF2501, PF2545, PF2547, PF2551, PF2553, PF2557, Z21101, Z21102, Z21106, Z21107, Z21111, Z21112, Z21113, Z21114, Z21115
This branch is defined by YFull as E-M81. There, it is the child of the E-M8 branch.
CTS87, CTS5883, CTS5567, CTS3442, CTS2116, CTS11147, CTS8527, CTS3700, CTS11333, PF2521, CTS3350, CTS6841, CTS7248, CTS6227, PF2499, PF2490, PF2486, PF2492, CTS1819, PF2500, CTS5974, PF2326, M81, CTS3415, CTS10321, CTS2587, CTS7132, PF2547, CTS4592, CTS10196, PF2489, PF2495, PF2501, CTS6518, PF2550, PF2493, Y7121, PF2401, M5300, M183, CTS2559, CTS6256, PF2551, PF2545, CTS3594, CTS11332, PF2506, CTS1294, CTS5229, CTS8121, PF2342, CTS5819, CTS5177, CTS4236, PF2558, PF2487, PF2485, PF2496, M5023, PF2304, BY699, Z21107, Z1168, CTS6645, CTS403, CTS11215, CTS2060, PF2549, PF2476, CTS8021, PF2556, Z21099, PF2555, PF2380, PF2474, PF2552, YP4760, M5351, M5350, M5349, M5348, M5338, M5347, M5339, M5346, M5345, Z1200, PF2488, PF2553, PF2480, CTS8282, PF2497, PF2478, PF2305, FGC22807, Z1203, CTS732, PF2473, CTS6820, PF2475, CTS12544, CTS1961, CTS9963, CTS6860, CTS5616, CTS665, M5358, CTS11467, PF2498, PF2491, CTS3870, CTS5039, PF2515, M5303, Z826, CTS9135, PF1453, PF2301, PF2479, CTS7349, PF2477, CTS1564, CTS12732, PF2311, CTS5021, CTS8464, FGC22814, CTS8854, PF2481, CTS12259, PF2306, PF2502, PF1470, CTS8570, M5364, PF1585, Z602, CTS6955, CTS10171, PF2310, FGC22809, M5094, PF2484, PF2557, PF2399, PF2415, PF2494, M5141, PF2327, PF2330
Peer reviewed sources have not been added for this branch yet. If you know of one I have missed, please link to it in the comments.