  We study the Euclidean supersymmetric D=11 M-algebras. We consider two such
D=11 superalgebras: the first one is N=(1,1) self-conjugate complex-Hermitean,
with 32 complex supercharges and 1024 real bosonic charges, the second is
N=(1,0) complex-holomorphic, with 32 complex supercharges and 528 bosonic
charges, which can be obtained by analytic continuation of known Minkowski
M-algebra. Due to the Bott's periodicity, we study at first the generic D=3
Euclidean supersymmetry case. The role of complex and quaternionic structures
for D=3 and D=11 Euclidean supersymmetry is elucidated. We show that the
additional 1024-528=496 Euclidean tensorial central charges are related with
the quaternionic structure of Euclidean D=11 supercharges, which in complex
notation satisfy SU(2) pseudo-Majorana condition. We consider also the
corresponding Osterwalder-Schrader conjugations as implying for N=(1,0) case
the reality of Euclidean bosonic charges. Finally, we outline some consequences
of our results, in particular for D=11 Euclidean supergravity.
