diff --git a/.github/actions/install/action.yml b/.github/actions/install/action.yml
index 8ba3dbbe57..54c1411d7f 100644
--- a/.github/actions/install/action.yml
+++ b/.github/actions/install/action.yml
@@ -17,6 +17,10 @@ inputs:
     description: Scalar type ('default' or 'complex')
     type: string
     default: default
+  int_type:
+    description: Integer type ('int32' or 'int64')
+    type: string
+    default: int32
   gpu:
     description: Target GPU platform
     type: string
@@ -53,6 +57,7 @@ runs:
           apt-get -y install \
             $(python3 ./firedrake-repo/scripts/firedrake-configure \
               --scalar-type ${{ inputs.scalar_type }} \
+              --int-type ${{ inputs.int_type }} \
               --gpu-arch ${{ inputs.gpu }} \
               --show-system-packages)
           : # Dependencies needed to run the test suite
@@ -66,6 +71,7 @@ runs:
           brew install \
             $(python3 ./firedrake-repo/scripts/firedrake-configure \
               --scalar-type ${{ inputs.scalar_type }} \
+              --int-type ${{ inputs.int_type }} \
               --show-system-packages)
         else
           echo "Unrecognised 'os' input: '${{ inputs.os }}"
@@ -101,6 +107,7 @@ runs:
         cd petsc
         python3 ../firedrake-repo/scripts/firedrake-configure \
           --scalar-type ${{ inputs.scalar_type }} \
+          --int-type ${{ inputs.int_type }} \
           --gpu-arch ${{ inputs.gpu }} \
           --show-petsc-configure-options | \
           xargs -L1 ./configure \
@@ -114,6 +121,7 @@ runs:
       run: |
         export $(python3 ./firedrake-repo/scripts/firedrake-configure \
           --scalar-type ${{ inputs.scalar_type }} \
+          --int-type ${{ inputs.int_type }} \
           --gpu-arch ${{ inputs.gpu }} \
           --show-env)
         export SLEPC_DIR=$PETSC_DIR/$PETSC_ARCH
diff --git a/.github/workflows/core.yml b/.github/workflows/core.yml
index b7db61e65e..b648bf2715 100644
--- a/.github/workflows/core.yml
+++ b/.github/workflows/core.yml
@@ -23,6 +23,10 @@ on:
         description: Whether to test a complex build
         type: boolean
         required: true
+      test_int64:
+        description: Whether to test a 64-bit integer build
+        type: boolean
+        required: true
       test_cuda:
         description: Whether to test using CUDA-enabled PETSc
         type: boolean
@@ -54,6 +58,10 @@ on:
         description: Whether to test a complex build
         type: boolean
         required: true
+      test_int64:
+        description: Whether to test a 64-bit integer build
+        type: boolean
+        required: true
       test_cuda:
         description: Whether to test using CUDA-enabled PETSc
         type: boolean
@@ -262,10 +270,18 @@ jobs:
         id: generate
         run: |
           if [ ${{ inputs.test_complex }} == 'true' ]; then
-            matrix='{"scalar_type": "complex", "gpu": "none"}'
+            matrix='{"scalar_type": "complex", "int_type": "int32", "gpu": "none"}'
+          fi
+          if [ ${{ inputs.test_int64 }} == 'true' ]; then
+            arch='{"scalar_type": "default", "int_type": "int64", "gpu": "none"}'
+            if [ "$matrix" ]; then
+              matrix="$matrix, $arch"
+            else
+              matrix="$arch"
+            fi
           fi
           if [ ${{ inputs.test_cuda }} == 'true' ]; then
-            arch='{"scalar_type": "default", "gpu": "cuda"}'
+            arch='{"scalar_type": "default", "int_type": "int32", "gpu": "cuda"}'
             if [ "$matrix" ]; then
               matrix="$matrix, $arch"
             else
@@ -319,6 +335,7 @@ jobs:
           source_ref: ${{ inputs.source_ref }}
           base_ref: ${{ inputs.base_ref }}
           scalar_type: ${{ matrix.scalar_type }}
+          int_type: ${{ matrix.int_type }}
           gpu: ${{ matrix.gpu }}
           deps: ci
 
diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
index 8f250c86f7..ad2665061d 100644
--- a/.github/workflows/pr.yml
+++ b/.github/workflows/pr.yml
@@ -23,6 +23,7 @@ jobs:
       # Run all tests of a specific configuration (e.g. complex) if the right label
       # is on the PR, otherwise do nothing.
       test_complex: ${{ contains(github.event.pull_request.labels.*.name, 'ci:complex') }}
+      test_int64: ${{ contains(github.event.pull_request.labels.*.name, 'ci:int64') }}
       test_cuda: ${{ contains(github.event.pull_request.labels.*.name, 'ci:cuda') }}
       test_macos: ${{ contains(github.event.pull_request.labels.*.name, 'ci:macos') }}
     secrets: inherit
diff --git a/.github/workflows/push.yml b/.github/workflows/push.yml
index 5719c624ff..f55da62a99 100644
--- a/.github/workflows/push.yml
+++ b/.github/workflows/push.yml
@@ -14,6 +14,7 @@ jobs:
       source_ref: ${{ github.ref_name }}
       base_ref: ${{ github.ref_name }}
       test_complex: true
+      test_int64: true
       test_cuda: true
       test_macos: true
       deploy_website: true
diff --git a/docs/source/install.rst b/docs/source/install.rst
index 01e58dc6d8..a9a94b47a5 100644
--- a/docs/source/install.rst
+++ b/docs/source/install.rst
@@ -413,16 +413,16 @@ Prepared configurations
 -----------------------
 
 ``firedrake-configure`` provides a number of different possible configurations
-(termed 'ARCHs') that specify how PETSc is configured and which external
-packages are built. The currently supported ARCHs are:
+that specify how PETSc is configured and which external packages are built. To
+select a non-default configuration you can pass extra flags to
+``firedrake-configure``. For example, to build Firedrake in complex mode you
+should pass ``--scalar-type complex``::
 
-* ``default``: the default installation, suitable for most users
-* ``complex``: an installation where PETSc is configured using complex numbers
+   $ python3 firedrake-configure --show-petsc-configure-options --scalar-type complex
 
-The different configurations can be selected by passing the flag ``--arch`` to
-``firedrake-configure``. For example::
+To see the full list of available options you should run::
 
-   $ python3 firedrake-configure --show-petsc-configure-options --arch complex
+   $ python3 firedrake-configure --help
 
 
 Optional dependencies
@@ -499,9 +499,9 @@ Since ``firedrake-configure`` only outputs a string of options it is straightfor
 to customise the options that are passed to PETSc ``configure``. You can either:
 
 * Append additional options when ``configure`` is invoked. For example, to
-  build PETSc with support for 64-bit indices you should run::
+  build PETSc with HPDDM you should run::
 
-   $ python3 ../firedrake-configure --show-petsc-configure-options | xargs -L1 ./configure --with-64-bit-indices
+   $ python3 ../firedrake-configure --show-petsc-configure-options | xargs -L1 ./configure --download-hpddm
 
 * Write the output of ``firedrake-configure`` to a file than can be modified. For example::
 
diff --git a/scripts/firedrake-configure b/scripts/firedrake-configure
index 4bcafad20e..9e2f45db55 100755
--- a/scripts/firedrake-configure
+++ b/scripts/firedrake-configure
@@ -72,9 +72,10 @@ def main():
 
     os_ = OS(args.os) if args.os else detect_os()
     scalar_type = ScalarType(args.scalar_type)
+    int_type = IntType(args.int_type)
     gpu_arch = GPUPlatform(args.gpu_arch)
 
-    arch_key = (os_, scalar_type, gpu_arch)
+    arch_key = (os_, scalar_type, int_type, gpu_arch)
     arch_key_str = f"{{{', '.join(f'{k.__class__.__name__}: {k.value}' for k in arch_key)}}}"
     if arch_key in OFFICIAL_ARCHS:
         arch = OFFICIAL_ARCHS[arch_key]
@@ -162,6 +163,12 @@ Please see https://firedrakeproject.org/install for more information."""
         default=ScalarType.DEFAULT.value,
         help="PETSc scalar type.",
     )
+    parser.add_argument(
+        "--int-type",
+        choices=[it.value for it in IntType],
+        default=IntType.INT32.value,
+        help="PETSc integer type.",
+    )
     parser.add_argument(
         "--gpu-arch",
         choices=[gpu_opt.value for gpu_opt in GPUPlatform],
@@ -250,6 +257,11 @@ class ScalarType(enum.Enum):
     COMPLEX = "complex"
 
 
+class IntType(enum.Enum):
+    INT32 = "int32"
+    INT64 = "int64"
+
+
 class GPUPlatform(enum.Enum):
     NO_GPU = "none"
     CUDA = "cuda"
@@ -401,14 +413,14 @@ class CommunityArch(Arch):
     """
 
 
-ArchKey = tuple[OS, ScalarType, GPUPlatform]
+ArchKey = tuple[OS, ScalarType, IntType, GPUPlatform]
 
 # Configurations with official support that are tested in CI
 OFFICIAL_ARCHS: Mapping[ArchKey, Arch] = {
 
     # Ubuntu 26.04 x86
 
-    (OS.UBUNTU_2604_X86_64, ScalarType.DEFAULT, GPUPlatform.NO_GPU): Arch(
+    (OS.UBUNTU_2604_X86_64, ScalarType.DEFAULT, IntType.INT32, GPUPlatform.NO_GPU): Arch(
         name="default",
         system_packages=[
             "bison",
@@ -470,7 +482,7 @@ OFFICIAL_ARCHS: Mapping[ArchKey, Arch] = {
         ],
     ),
 
-    (OS.UBUNTU_2604_X86_64, ScalarType.COMPLEX, GPUPlatform.NO_GPU): Arch(
+    (OS.UBUNTU_2604_X86_64, ScalarType.COMPLEX, IntType.INT32, GPUPlatform.NO_GPU): Arch(
         name="complex",
         system_packages=[
             "bison",
@@ -530,9 +542,65 @@ OFFICIAL_ARCHS: Mapping[ArchKey, Arch] = {
         ],
     ),
 
+    (OS.UBUNTU_2604_X86_64, ScalarType.DEFAULT, IntType.INT64, GPUPlatform.NO_GPU): Arch(
+        name="int64",
+        system_packages=[
+            "bison",
+            "build-essential",
+            "cmake",
+            "flex",
+            "gfortran",
+            "git",
+            "ninja-build",
+            "pkg-config",
+            "python3-dev",
+            "python3-pip",
+
+            # PETSc external packages
+            "libfftw3-dev",
+            "libfftw3-mpi-dev",
+            "libhdf5-mpi-dev",
+            "libhwloc-dev",
+            "libnetcdf-dev",
+            "libopenblas-dev",
+            "libopenmpi-dev",
+            "libpnetcdf-dev",
+            "libscalapack-openmpi-dev",
+            "libsuitesparse-dev",
+            "libsuperlu-dev",
+        ],
+        extra_petsc_configure_options=[
+            "--with-64-bit-indices",
+            "--with-bison",
+            "--with-fftw",
+            "--with-hdf5",
+            "--with-hwloc",
+            "--download-hypre",
+            "--download-metis",
+            "--download-mumps",
+            "--with-netcdf",
+            "--with-pnetcdf",
+            "--download-ptscotch",
+            "--with-scalapack-lib=-lscalapack-openmpi",
+            "--with-suitesparse",
+            "--download-superlu_dist",
+            "--with-zlib",
+        ],
+        cflags=["-O3", "-march=native", "-mtune=native"],
+        cxxflags=["-O3", "-march=native", "-mtune=native"],
+        fflags=["-O3", "-march=native", "-mtune=native"],
+        include_dirs=[
+            "/usr/include/hdf5/openmpi",
+            "/usr/include/superlu",
+        ],
+        library_dirs=[
+            "/usr/lib/x86_64-linux-gnu/hdf5/openmpi",
+        ],
+    ),
+
     # Ubuntu 26.04 aarch64
 
-    (OS.UBUNTU_2604_AARCH64, ScalarType.DEFAULT, GPUPlatform.NO_GPU): Arch(
+    (OS.UBUNTU_2604_AARCH64, ScalarType.DEFAULT, IntType.INT32, GPUPlatform.NO_GPU): Arch(
         name="default",
         system_packages=[
             "bison",
@@ -594,7 +662,7 @@ OFFICIAL_ARCHS: Mapping[ArchKey, Arch] = {
         ],
     ),
 
-    (OS.UBUNTU_2604_AARCH64, ScalarType.COMPLEX, GPUPlatform.NO_GPU): Arch(
+    (OS.UBUNTU_2604_AARCH64, ScalarType.COMPLEX, IntType.INT32, GPUPlatform.NO_GPU): Arch(
         name="complex",
         system_packages=[
             "bison",
@@ -656,7 +724,7 @@ OFFICIAL_ARCHS: Mapping[ArchKey, Arch] = {
 
     # Ubuntu 26.04 x86 CUDA
 
-    (OS.UBUNTU_2404_X86_64, ScalarType.DEFAULT, GPUPlatform.CUDA): Arch(
+    (OS.UBUNTU_2404_X86_64, ScalarType.DEFAULT, IntType.INT32, GPUPlatform.CUDA): Arch(
         name="default-cuda",
         system_packages=[
             "bison",
@@ -736,7 +804,7 @@ OFFICIAL_ARCHS: Mapping[ArchKey, Arch] = {
 
     # macOS arm64
 
-    (OS.MACOS_ARM64, ScalarType.DEFAULT, GPUPlatform.NO_GPU): Arch(
+    (OS.MACOS_ARM64, ScalarType.DEFAULT, IntType.INT32, GPUPlatform.NO_GPU): Arch(
         name="default",
         system_packages=[
             "autoconf",
@@ -789,7 +857,7 @@ OFFICIAL_ARCHS: Mapping[ArchKey, Arch] = {
         extra_env_vars={"HDF5_DIR": "/opt/homebrew"},
     ),
 
-    (OS.MACOS_ARM64, ScalarType.COMPLEX, GPUPlatform.NO_GPU): Arch(
+    (OS.MACOS_ARM64, ScalarType.COMPLEX, IntType.INT32, GPUPlatform.NO_GPU): Arch(
         name="complex",
         system_packages=[
             "autoconf",
@@ -845,7 +913,7 @@ OFFICIAL_ARCHS: Mapping[ArchKey, Arch] = {
 
     # Sane default configurations for unknown platforms
 
-    (OS.UNKNOWN, ScalarType.DEFAULT, GPUPlatform.NO_GPU): Arch(
+    (OS.UNKNOWN, ScalarType.DEFAULT, IntType.INT32, GPUPlatform.NO_GPU): Arch(
         name="default",
         extra_petsc_configure_options=[
             "--download-bison",
@@ -872,7 +940,7 @@ OFFICIAL_ARCHS: Mapping[ArchKey, Arch] = {
         },
     ),
 
-    (OS.UNKNOWN, ScalarType.COMPLEX, GPUPlatform.NO_GPU): Arch(
+    (OS.UNKNOWN, ScalarType.COMPLEX, IntType.INT32, GPUPlatform.NO_GPU): Arch(
         name="complex",
         extra_petsc_configure_options=[
             "--with-scalar-type=complex",
@@ -899,6 +967,34 @@ OFFICIAL_ARCHS: Mapping[ArchKey, Arch] = {
             "CC": "mpicc",
         },
     ),
+
+    (OS.UNKNOWN, ScalarType.DEFAULT, IntType.INT64, GPUPlatform.NO_GPU): Arch(
+        name="int64",
+        extra_petsc_configure_options=[
+            "--with-64-bit-indices",
+            "--download-bison",
+            "--download-fftw",
+            "--download-hdf5",
+            "--download-hwloc",
+            "--download-hypre",
+            "--download-metis",
+            "--download-mumps",
+            "--download-netcdf",
+            "--download-pnetcdf",
+            "--download-ptscotch",
+            "--download-scalapack",
+            "--download-suitesparse",
+            "--download-superlu_dist",
+            "--download-zlib",
+        ],
+        cflags=["-O3", "-march=native", "-mtune=native"],
+        cxxflags=["-O3", "-march=native", "-mtune=native"],
+        fflags=["-O3", "-march=native", "-mtune=native"],
+        extra_env_vars={
+            "HDF5_DIR": "$PETSC_DIR/$PETSC_ARCH",
+            "CC": "mpicc",
+        },
+    ),
 }
 
 
@@ -908,7 +1004,7 @@ RETIRED_ARCHS: Mapping[ArchKey, RetiredArch] = {
 
     # Ubuntu 24.04 x86
 
-    (OS.UBUNTU_2404_X86_64, ScalarType.DEFAULT, GPUPlatform.NO_GPU): RetiredArch(
+    (OS.UBUNTU_2404_X86_64, ScalarType.DEFAULT, IntType.INT32, GPUPlatform.NO_GPU): RetiredArch(
         name="default",
         last_modified="2026-05-13",
         system_packages=[
@@ -970,7 +1066,7 @@ RETIRED_ARCHS: Mapping[ArchKey, RetiredArch] = {
         ],
     ),
 
-    (OS.UBUNTU_2404_X86_64, ScalarType.COMPLEX, GPUPlatform.NO_GPU): RetiredArch(
+    (OS.UBUNTU_2404_X86_64, ScalarType.COMPLEX, IntType.INT32, GPUPlatform.NO_GPU): RetiredArch(
         name="complex",
         last_modified="2026-05-13",
         system_packages=[
@@ -1034,7 +1130,7 @@ RETIRED_ARCHS: Mapping[ArchKey, RetiredArch] = {
 
     # Ubuntu 24.04 aarch64
 
-    (OS.UBUNTU_2404_AARCH64, ScalarType.DEFAULT, GPUPlatform.NO_GPU): RetiredArch(
+    (OS.UBUNTU_2404_AARCH64, ScalarType.DEFAULT, IntType.INT32, GPUPlatform.NO_GPU): RetiredArch(
         name="default",
         last_modified="2026-05-13",
         system_packages=[
@@ -1096,7 +1192,7 @@ RETIRED_ARCHS: Mapping[ArchKey, RetiredArch] = {
         ],
     ),
 
-    (OS.UBUNTU_2404_AARCH64, ScalarType.COMPLEX, GPUPlatform.NO_GPU): RetiredArch(
+    (OS.UBUNTU_2404_AARCH64, ScalarType.COMPLEX, IntType.INT32, GPUPlatform.NO_GPU): RetiredArch(
         name="complex",
         last_modified="2026-05-13",
         system_packages=[