Special Lagrangian m-folds (SL m-folds) are a distinguished class of real mdimensional minimal submanifolds which may be defined in C m , or in CalabiYau m-folds, or more generally in almost Calabi-Yau m-folds (compact Kähler m-folds with trivial canonical bundle). We write an almost Calabi-Yau m-fold as M or (M, J, ω, Ω), where the manifold M has complex structure J, Kähler form ω and holomorphic volume form Ω. This is the third in a series of five papers [10,11,12,13] studying SL m-folds with isolated conical singularities. That is, we consider an SL m-fold X in an almost Calabi-Yau m-fold M for m > 2 with singularities at x 1 , . . . , x n in M , such that for some special Lagrangian cones C i in T xi M ∼ = C m with C i \ {0} nonsingular, X approaches C i near x i in an asymptotic C 1 sense. Readers are advised to begin with the final paper [13], which surveys the series, and applies the results to prove some conjectures.The first paper [10] laid the foundations for the series, and studied the regularity of SL m-folds with conical singularities near their singular points. The second paper [11] discussed the deformation theory of compact SL m-folds X with conical singularities in an almost Calabi-Yau m-fold M . This paper and the sequel [12] study desingularizations of compact SL mfolds X with conical singularities. That is, we construct a family of compact, nonsingular SL m-foldsÑ t in M for t ∈ (0, ǫ] such thatÑ t → X as t → 0, in the sense of currents.Having a good understanding of the singularities of special Lagrangian submanifolds will be essential in clarifying the Strominger-Yau-Zaslow conjecture on the Mirror Symmetry of Calabi-Yau 3-folds [20], and also in resolving conjectures made by the author [7] on defining new invariants of Calabi-Yau 3-folds by counting special Lagrangian homology 3-spheres with weights. The series aims to develop such an understanding for simple singularities of SL m-folds.Here is the basic idea of the paper. Let X be a compact SL m-fold with conical singularities x 1 , . . . , x n in an almost Calabi-Yau m-fold (M, J, ω, Ω).
1Choose an isomorphism υ i : C m → T xi M for i = 1, . . . , n. Then there is a unique SL cone C i in C m with X asymptotic to υ i (C i ) at x i . Let L i be an Asymptotically Conical SL m-fold (AC SL m-fold ) in C m , asymptotic to C i at infinity. As C i is a cone it is invariant under dilations, so tC i = C i for all t > 0. Thus tL i = {t x : x ∈ L i } is also an AC SL m-fold asymptotic to C i for t > 0. We explicitly construct a 1-parameter family of compact, nonsingular Lagrangian m-folds N t in (M, ω) for t ∈ (0, δ) by gluing tL i into X at x i , using a partition of unity.When t is small, N t is close to being special Lagrangian (its phase is nearly constant), but also close to being singular (it has large curvature and small injectivity radius). We prove using analysis that for small ǫ ∈ (0, δ) we can deform N t to a special Lagrangian m-foldÑ t in M for all t ∈ (0, ǫ], using a small Hamiltonian deformation. The proof involves a delicate balancin...