diff --git a/CHANGELOG.md b/CHANGELOG.md
index dbbbba38..b5a46bf3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - `--help-list-offsets` to list footprint offsets (JLCPCB)
   - `--help-list-rotations` to list footprint rotations (JLCPCB)
   - `--stop-on-warnings` (`-W`) to stop on warnings (#545)
+  - `--defs-from-env` allows using environment vars for substitution (#549)
 - Global options:
   - `remove_solder_mask_for_dnp` similar to `remove_solder_paste_for_dnp` but
     applied to the solder mask apertures. (#476)
diff --git a/docs/source/configuration/substitution.rst b/docs/source/configuration/substitution.rst
index 3a4a3422..96efee35 100644
--- a/docs/source/configuration/substitution.rst
+++ b/docs/source/configuration/substitution.rst
@@ -24,6 +24,8 @@ files.
 
 You can use ``-E`` as many times as you need.
 
+Also note that the ``--def-from-env`` option adds all the environment
+variables as definitions.
 
 .. index::
    pair: definitions; default
diff --git a/docs/source/usage.txt b/docs/source/usage.txt
index bdbdcaff..caf9484b 100644
--- a/docs/source/usage.txt
+++ b/docs/source/usage.txt
@@ -3,10 +3,11 @@ KiBot: KiCad automation tool for documents generation
 Usage:
   kibot [-b BOARD] [-e SCHEMA] [-c CONFIG] [-d OUT_DIR] [-s PRE]
          [-q | -v...] [-L LOGFILE] [-C | -i | -n] [-m MKFILE] [-A] [-g DEF] ...
-         [-E DEF] ... [-w LIST] [-D | -W] [--banner N] [TARGET...]
+         [-E DEF] ... [--defs-from-env] [-w LIST] [-D | -W] [--banner N]
+         [TARGET...]
   kibot [-v...] [-b BOARD] [-e SCHEMA] [-c PLOT_CONFIG] [--banner N]
-         [-E DEF] ... [--config-outs] [--only-pre|--only-groups] [--only-names]
-         [--output-name-first] --list
+         [-E DEF] ... [--defs-from-env] [--config-outs]
+         [--only-pre|--only-groups] [--only-names] [--output-name-first] --list
   kibot [-v...] [-c PLOT_CONFIG] [--banner N] [-E DEF] ... [--only-names]
          --list-variants
   kibot [-v...] [-b BOARD] [-d OUT_DIR] [-p | -P] [--banner N] --example
@@ -39,6 +40,8 @@ Options:
   --config-outs                    Configure all outputs before listing them
   -d OUT_DIR, --out-dir OUT_DIR    The output directory [default: .]
   -D, --dont-stop                  Try to continue if an output fails
+  --defs-from-env                  Use the environment vars as preprocessor
+                                   values
   -e SCHEMA, --schematic SCHEMA    The schematic file (.sch/.kicad_sch)
   -E DEF, --define DEF             Define preprocessor value (VAR=VAL)
   -g DEF, --global-redef DEF       Overwrite a global value (VAR=VAL)
diff --git a/kibot/__main__.py b/kibot/__main__.py
index a6655a23..7dee3fef 100644
--- a/kibot/__main__.py
+++ b/kibot/__main__.py
@@ -10,10 +10,11 @@
 Usage:
   kibot [-b BOARD] [-e SCHEMA] [-c CONFIG] [-d OUT_DIR] [-s PRE]
          [-q | -v...] [-L LOGFILE] [-C | -i | -n] [-m MKFILE] [-A] [-g DEF] ...
-         [-E DEF] ... [-w LIST] [-D | -W] [--banner N] [TARGET...]
+         [-E DEF] ... [--defs-from-env] [-w LIST] [-D | -W] [--banner N]
+         [TARGET...]
   kibot [-v...] [-b BOARD] [-e SCHEMA] [-c PLOT_CONFIG] [--banner N]
-         [-E DEF] ... [--config-outs] [--only-pre|--only-groups] [--only-names]
-         [--output-name-first] --list
+         [-E DEF] ... [--defs-from-env] [--config-outs]
+         [--only-pre|--only-groups] [--only-names] [--output-name-first] --list
   kibot [-v...] [-c PLOT_CONFIG] [--banner N] [-E DEF] ... [--only-names]
          --list-variants
   kibot [-v...] [-b BOARD] [-d OUT_DIR] [-p | -P] [--banner N] --example
@@ -46,6 +47,8 @@
   --config-outs                    Configure all outputs before listing them
   -d OUT_DIR, --out-dir OUT_DIR    The output directory [default: .]
   -D, --dont-stop                  Try to continue if an output fails
+  --defs-from-env                  Use the environment vars as preprocessor
+                                   values
   -e SCHEMA, --schematic SCHEMA    The schematic file (.sch/.kicad_sch)
   -E DEF, --define DEF             Define preprocessor value (VAR=VAL)
   -g DEF, --global-redef DEF       Overwrite a global value (VAR=VAL)
@@ -340,6 +343,8 @@ def detect_kicad():
 
 
 def parse_defines(args):
+    if args.defs_from_env:
+        GS.cli_defines.update(os.environ)
     for define in args.define:
         if '=' not in define:
             GS.exit_with_error(f'Malformed `define` option, must be VARIABLE=VALUE ({define})', EXIT_BAD_ARGS)