diff --git a/src/hsl_mc66.jl b/src/hsl_mc66.jl
new file mode 100644
index 0000000..3308a5d
--- /dev/null
+++ b/src/hsl_mc66.jl
@@ -0,0 +1,102 @@
+export mc66, mc66_control
+
+mutable struct fa14_seed
+  ix::Int32
+end
+
+fa14_seed() = fa14_seed(65535)
+
+mutable struct mc66_control{T <: BLAS.BlasReal}
+  lp::Int32
+  wp::Int32
+  mp::Int32
+  print_level::Int32
+  kl_aggressive::T
+  max_imbalance::T
+  mglevel::Int32
+  grid_rdc_fac::T
+  coarsest_size::Int32
+  coarsen_scheme::Int32
+  num_coarsest_kl::Int32
+end
+
+function mc66_control{T}(; lp=6, wp=6, mp=6, print_level=-1, kl_aggressive=-1, max_imbalance=0.01,
+                           mglevel=typemax(Int32), grid_rdc_fac=0.75, coarsest_size=100,
+                           coarsen_scheme=1, num_coarsest_kl=4) where {T <: BLAS.BlasReal}
+
+  control = mc66_control{T}(lp, wp, mp, print_level, kl_aggressive, max_imbalance, mglevel,
+                            grid_rdc_fac, coarsest_size, coarsen_scheme, num_coarsest_kl)
+  return control
+end
+
+#! format: off
+# Thanks to `nm -D libhsl_mc66.so`!
+function mc66s(m, n, nz, irn, jcn, nblocks, control, seed, row_order, info, rowptr, column_order, colptr, netcut, rowdiff, kblocks)
+  ccall((:__hsl_mc66_simple_MOD_monet, libhsl_mc66),
+        Cvoid,
+        (Ref{Int32}, Ref{Int32}, Ref{Int32}, Ptr{Int32}, Ptr{Int32}, Ref{Int32}, Ref{mc66_control{Float32}}, Ref{fa14_seed}, Ptr{Int32}, Ref{Int32}, Ptr{Int32}, Ptr{Int32}  , Ptr{Int32}, Ref{Int32}, Ref{Float32}, Ref{Int32}),
+         m         , n         , nz        , irn       , jcn       , nblocks   , control                   , seed          , row_order , info      , rowptr    , column_order, colptr    , netcut    , rowdiff     , kblocks   )
+end
+
+function mc66s_print_message(info)
+  lp = Ref{Int32}(6)
+  wp = Ref{Int32}(6)
+  context = Ptr{Cvoid}()
+  ccall((:__hsl_mc66_single_MOD_monet_print_message, libhsl_mc66),
+        Cvoid,
+        (Ref{Int32}, Ref{Int32}, Ref{Int32}, Cstring),
+        info       , lp        , wp        , context)
+end
+
+function mc66d(m, n, nz, irn, jcn, nblocks, control, seed, row_order, info, rowptr, column_order, colptr, netcut, rowdiff, kblocks)
+  ccall((:__hsl_mc66_double_MOD_monet, libhsl_mc66),
+        Cvoid,
+        (Ref{Int32}, Ref{Int32}, Ref{Int32}, Ptr{Int32}, Ptr{Int32}, Ref{Int32}, Ref{mc66_control{Float64}}, Ref{fa14_seed}, Ptr{Int32}, Ref{Int32}, Ptr{Int32}, Ptr{Int32}  , Ptr{Int32}, Ref{Int32}, Ref{Float64}, Ref{Int32}),
+         m         , n         , nz        , irn       , jcn       , nblocks   , control                   , seed          , row_order , info      , rowptr    , column_order, colptr    , netcut    , rowdiff     , kblocks   )
+end
+
+function mc66d_print_message(info, control)
+  context = Ptr{Cvoid}()
+  ccall((:__hsl_mc66_double_MOD_monet_print_message, libhsl_mc66),
+        Cvoid,
+        (Ref{Int32}, Ref{Int32}, Ref{Int32}, Cstring),
+        info       , control.lp, control.wp, context)
+end
+#! format: on
+
+"""
+    rp, cp = mc66(A::SparseMatrixCSC, k::Integer)
+
+Order an unsymmetric matrix A into singly bordered blocked diagonal (SBBD) form.
+
+    A[rp, cp] = [ A₁₁                  S₁]
+                [     A₂₂              S₂]
+                [          •           • ]
+                [             •        • ]
+                [                •     • ]
+                [                  Aₖₖ Sₖ]
+"""
+function mc66(A::SparseMatrixCSC, nblocks::Integer)
+  m, n = size(A)
+  nblocks ≤ min(m,n) || error("1 ≤ nblocks ≤ min(m,n)")
+  m = Ref{Int32}(m)
+  n = Ref{Int32}(n)
+  nz = Ref{Int32}(nnz(A))
+  irn, jcn, val = findnz(A)
+  irn = convert(Vector{Cint}, irn)
+  jcn = convert(Vector{Cint}, jcn)
+  nblocks = Ref{Int32}(nblocks)
+  control = mc66_control{Float64}()
+  seed = fa14_seed()
+  row_order = zeros(Cint, m[])
+  info = Ref{Cint}()
+  rowptr = zeros(Cint, nblocks[]+1)
+  column_order = zeros(Cint, n[])
+  colptr = zeros(Cint, nblocks[]+1)
+  netcut = Ref{Cint}()
+  rowdiff = Ref{Float64}()
+  kblocks = Ref{Cint}()
+  mc66d(m, n, nz, irn, jcn, nblocks, control, seed, row_order, info, rowptr, column_order, colptr, netcut, rowdiff, kblocks)
+  mc66d_print_message(info[], control)
+  return row_order, column_order
+end
diff --git a/test/test_hsl_mc66.jl b/test/test_hsl_mc66.jl
new file mode 100644
index 0000000..bd1b6ed
--- /dev/null
+++ b/test/test_hsl_mc66.jl
@@ -0,0 +1,18 @@
+@testset "hsl_mc66" begin
+  #! format: off
+  A = [1 1 0 0;
+       1 0 1 1;
+       1 1 0 0;
+       1 0 1 1]
+
+  B = [1 0 0 1;
+       1 0 0 1;
+       0 1 1 1;
+       0 1 1 1]
+  #! format: on
+  C = SparseMatrixCSC(A)
+  rp, cp = mc66(C, 2)
+  @test isperm(rp)
+  @test isperm(cp)
+  @test A[rp,cp] == B
+end