diff --git a/base/array.jl b/base/array.jl
index 5911a8fbaf0eac..9bdee6d55c2cc1 100644
--- a/base/array.jl
+++ b/base/array.jl
@@ -214,7 +214,7 @@ function bitsunionsize(u::Union)
 end
 
 length(a::Array) = arraylen(a)
-elsize(::Type{<:Array{T}}) where {T} = isbitstype(T) ? sizeof(T) : (isbitsunion(T) ? bitsunionsize(T) : sizeof(Ptr))
+elsize(::Type{<:Array{T}}) where {T} = aligned_sizeof(T)
 sizeof(a::Array) = Core.sizeof(a)
 
 function isassigned(a::Array, i::Int...)
@@ -240,7 +240,7 @@ function unsafe_copyto!(dest::Ptr{T}, src::Ptr{T}, n) where T
     # Do not use this to copy data between pointer arrays.
     # It can't be made safe no matter how carefully you checked.
     ccall(:memmove, Ptr{Cvoid}, (Ptr{Cvoid}, Ptr{Cvoid}, UInt),
-          dest, src, n*sizeof(T))
+          dest, src, n * aligned_sizeof(T))
     return dest
 end
 
@@ -261,7 +261,7 @@ function unsafe_copyto!(dest::Array{T}, doffs, src::Array{T}, soffs, n) where T
         unsafe_copyto!(pointer(dest, doffs), pointer(src, soffs), n)
     elseif isbitsunion(T)
         ccall(:memmove, Ptr{Cvoid}, (Ptr{Cvoid}, Ptr{Cvoid}, UInt),
-              pointer(dest, doffs), pointer(src, soffs), n * Base.bitsunionsize(T))
+              pointer(dest, doffs), pointer(src, soffs), n * aligned_sizeof(T))
         # copy selector bytes
         ccall(:memmove, Ptr{Cvoid}, (Ptr{Cvoid}, Ptr{Cvoid}, UInt),
               ccall(:jl_array_typetagdata, Ptr{UInt8}, (Any,), dest) + doffs - 1,
@@ -1549,14 +1549,10 @@ function vcat(arrays::Vector{T}...) where T
     end
     arr = Vector{T}(undef, n)
     ptr = pointer(arr)
-    if isbitstype(T)
-        elsz = Core.sizeof(T)
-    elseif isbitsunion(T)
-        elsz = bitsunionsize(T)
+    if isbitsunion(T)
         selptr = ccall(:jl_array_typetagdata, Ptr{UInt8}, (Any,), arr)
-    else
-        elsz = Core.sizeof(Ptr{Cvoid})
     end
+    elsz = aligned_sizeof(T)
     t = @_gc_preserve_begin arr
     for a in arrays
         na = length(a)
diff --git a/base/reflection.jl b/base/reflection.jl
index dc87a42e0f247a..0b5a755b40a355 100644
--- a/base/reflection.jl
+++ b/base/reflection.jl
@@ -337,6 +337,23 @@ function datatype_alignment(dt::DataType)
     return Int(alignment & 0x1FF)
 end
 
+# amount of total space taken by T when stored in a container
+function aligned_sizeof(T)
+    @_pure_meta
+    if isbitsunion(T)
+        sz = Ref{Csize_t}(0)
+        algn = Ref{Csize_t}(0)
+        ccall(:jl_islayout_inline, Cint, (Any, Ptr{Csize_t}, Ptr{Csize_t}), T, sz, algn)
+        al = algn[]
+        return (sz[] + al - 1) & -al
+    elseif allocatedinline(T)
+        al = datatype_alignment(T)
+        return (Core.sizeof(T) + al - 1) & -al
+    else
+        return Core.sizeof(Ptr{Cvoid})
+    end
+end
+
 gc_alignment(sz::Integer) = Int(ccall(:jl_alignment, Cint, (Csize_t,), sz))
 gc_alignment(T::Type) = gc_alignment(Core.sizeof(T))
 
diff --git a/src/array.c b/src/array.c
index c5af42736451c2..a0627ff24ab8e5 100644
--- a/src/array.c
+++ b/src/array.c
@@ -156,6 +156,9 @@ static inline jl_array_t *_new_array(jl_value_t *atype, uint32_t ndims, size_t *
         elsz = sizeof(void*);
         al = elsz;
     }
+    else {
+        elsz = LLT_ALIGN(elsz, al);
+    }
 
     return _new_array_(atype, ndims, dims, isunboxed, isunion, elsz);
 }
@@ -207,7 +210,7 @@ JL_DLLEXPORT jl_array_t *jl_reshape_array(jl_value_t *atype, jl_array_t *data,
     int isboxed = !jl_islayout_inline(eltype, &elsz, &align);
     assert(isboxed == data->flags.ptrarray);
     if (!isboxed) {
-        a->elsize = elsz;
+        a->elsize = LLT_ALIGN(elsz, align);
         jl_value_t *ownerty = jl_typeof(owner);
         size_t oldelsz = 0, oldalign = 0;
         if (ownerty == (jl_value_t*)jl_string_type) {
@@ -323,7 +326,7 @@ JL_DLLEXPORT jl_array_t *jl_ptr_to_array_1d(jl_value_t *atype, void *data,
 #ifdef STORE_ARRAY_LEN
     a->length = nel;
 #endif
-    a->elsize = elsz;
+    a->elsize = LLT_ALIGN(elsz, align);
     a->flags.ptrarray = !isunboxed;
     a->flags.ndims = 1;
     a->flags.isshared = 1;
@@ -389,7 +392,7 @@ JL_DLLEXPORT jl_array_t *jl_ptr_to_array(jl_value_t *atype, void *data,
 #ifdef STORE_ARRAY_LEN
     a->length = nel;
 #endif
-    a->elsize = elsz;
+    a->elsize = LLT_ALIGN(elsz, align);
     a->flags.ptrarray = !isunboxed;
     a->flags.ndims = ndims;
     a->offset = 0;
diff --git a/src/julia.h b/src/julia.h
index 4d55398895bd53..2ff686ca6fff5d 100644
--- a/src/julia.h
+++ b/src/julia.h
@@ -173,7 +173,7 @@ JL_EXTENSION typedef struct {
     size_t length;
 #endif
     jl_array_flags_t flags;
-    uint16_t elsize;
+    uint16_t elsize;  // element size including alignment (dim 1 memory stride)
     uint32_t offset;  // for 1-d only. does not need to get big.
     size_t nrows;
     union {
diff --git a/test/core.jl b/test/core.jl
index 06e7c4a900732c..a58f0d7d3f98c6 100644
--- a/test/core.jl
+++ b/test/core.jl
@@ -6456,6 +6456,31 @@ let A=[0, missing], B=[missing, 0], C=Vector{Union{Int, Missing}}(undef, 6)
     @test isequal(C, [0, missing, missing, missing, 0, missing])
 end
 
+# non-power-of-2 element sizes, issue #26026
+primitive type TypeWith24Bits 24 end
+TypeWith24Bits(x::UInt32) = Core.Intrinsics.trunc_int(TypeWith24Bits, x)
+let x = TypeWith24Bits(0x112233), y = TypeWith24Bits(0x445566), z = TypeWith24Bits(0x778899)
+    a = [x, x]
+    Core.arrayset(true, a, y, 2)
+    @test a == [x, y]
+    a[2] = z
+    @test a == [x, z]
+    @test pointer(a, 2) - pointer(a, 1) == 4
+
+    b = [(x, x), (x, x)]
+    Core.arrayset(true, b, (x, y), 2)
+    @test b == [(x, x), (x, y)]
+    b[2] = (y, z)
+    @test b == [(x, x), (y, z)]
+
+    V = Vector{TypeWith24Bits}(undef, 1000)
+    p = Ptr{UInt8}(pointer(V))
+    for i = 1:sizeof(V)
+        unsafe_store!(p, i % UInt8, i)
+    end
+    @test V[1:4] == [TypeWith24Bits(0x030201), TypeWith24Bits(0x070605), TypeWith24Bits(0x0b0a09), TypeWith24Bits(0x0f0e0d)]
+end
+
 # issue #29718
 function f29718()
     nt = NamedTuple{(:a, :b, :c, :d, :e, :f,),