diff --git a/esphome/components/esp8266/__init__.py b/esphome/components/esp8266/__init__.py
index e4d8dfc492..d0d870c289 100644
--- a/esphome/components/esp8266/__init__.py
+++ b/esphome/components/esp8266/__init__.py
@@ -114,9 +114,37 @@ _validate_toolchain = cv.toolchain_enum(_TOOLCHAINS)
 _resolve_toolchain = cv.resolve_toolchain("ESP8266", _TOOLCHAINS, Toolchain.ARDUINO)
 
 
+# Known boards keyed by spelling with case and "-" / "_" folded away
+_FOLDED_BOARDS = {board.lower().replace("-", "_"): board for board in BOARDS}
+
+
+def _resolve_board(config: ConfigType) -> ConfigType:
+    """Fix a misspelled board, else build an unknown one with PlatformIO."""
+    board = config[CONF_BOARD]
+    if board in BOARDS:
+        return config
+    if canonical := _FOLDED_BOARDS.get(board.lower().replace("-", "_")):
+        _LOGGER.warning(
+            "Board '%s' is not a known ESP8266 board; using '%s'", board, canonical
+        )
+        return {**config, CONF_BOARD: canonical}
+    if CORE.toolchain is None and CONF_TOOLCHAIN not in config:
+        return {**config, CONF_TOOLCHAIN: Toolchain.PLATFORMIO}
+    return config
+
+
 def _warn_platformio_toolchain(config: ConfigType) -> ConfigType:
     # Remove before 2027.4.0
-    if CORE.using_toolchain_platformio:
+    if not CORE.using_toolchain_platformio:
+        return config
+    if config[CONF_BOARD] not in BOARDS:
+        _LOGGER.warning(
+            "Board '%s' is not supported by the native 'arduino' toolchain, so it "
+            "builds with the deprecated 'platformio' toolchain, which will be "
+            "removed in ESPHome 2027.4.0",
+            config[CONF_BOARD],
+        )
+    else:
         _LOGGER.warning(
             "The 'platformio' toolchain for ESP8266 is deprecated and will be "
             "removed in ESPHome 2027.4.0; the native 'arduino' toolchain is the "
@@ -329,6 +357,7 @@ CONFIG_SCHEMA = cv.All(
             ): _validate_toolchain,
         }
     ),
+    _resolve_board,
     _resolve_toolchain,
     _warn_platformio_toolchain,
     _validate_native_toolchain,
diff --git a/tests/unit_tests/components/esp8266/test_toolchain_validation.py b/tests/unit_tests/components/esp8266/test_toolchain_validation.py
index e7f443c2d2..1092c168ad 100644
--- a/tests/unit_tests/components/esp8266/test_toolchain_validation.py
+++ b/tests/unit_tests/components/esp8266/test_toolchain_validation.py
@@ -12,10 +12,12 @@ import pytest
 from esphome.components import esp8266
 from esphome.components.esp8266 import (
     ARDUINO_FRAMEWORK_SCHEMA,
+    _resolve_board,
     _resolve_toolchain,
     _validate_native_toolchain,
     _warn_platformio_toolchain,
 )
+from esphome.components.esp8266.const import KEY_BOARD, KEY_ESP8266
 import esphome.config_validation as cv
 from esphome.const import (
     CONF_BOARD,
@@ -118,6 +120,57 @@ def test_unsupported_board_rejected() -> None:
         _validate_native_toolchain(_config(board="not_a_board"))
 
 
+def test_known_board_passes_unchanged() -> None:
+    config = {CONF_BOARD: "esp01_1m"}
+    assert _resolve_board(config) is config
+
+
+@pytest.mark.parametrize(
+    ("board", "expected"),
+    [("ESP01-1M", "esp01_1m"), ("SPARKFUNBLYNK", "sparkfunBlynk")],
+)
+def test_misspelled_board_normalized(
+    board: str, expected: str, caplog: pytest.LogCaptureFixture
+) -> None:
+    assert _resolve_board({CONF_BOARD: board})[CONF_BOARD] == expected
+    assert f"using '{expected}'" in caplog.text
+
+
+@pytest.mark.parametrize(
+    ("board", "expected_board", "expected_toolchain"),
+    [
+        ("esp01-1m", "esp01_1m", Toolchain.ARDUINO),
+        ("my_custom_board", "my_custom_board", Toolchain.PLATFORMIO),
+    ],
+)
+def test_config_schema_resolves_board_before_toolchain(
+    board: str,
+    expected_board: str,
+    expected_toolchain: Toolchain,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """The full chain normalizes or falls back, and warns once."""
+    CORE.toolchain = None
+    config = esp8266.CONFIG_SCHEMA({CONF_BOARD: board})
+    assert config[CONF_BOARD] == expected_board
+    assert CORE.data[KEY_ESP8266][KEY_BOARD] == expected_board
+    assert CORE.toolchain == expected_toolchain
+    assert len(caplog.records) == 1
+
+
+@pytest.mark.parametrize(
+    ("cli_toolchain", "yaml"),
+    [(Toolchain.ARDUINO, {}), (None, {CONF_TOOLCHAIN: Toolchain.ARDUINO})],
+)
+def test_unknown_board_keeps_explicit_toolchain(
+    cli_toolchain: Toolchain | None, yaml: ConfigType
+) -> None:
+    """A CLI or YAML toolchain is not overridden."""
+    CORE.toolchain = cli_toolchain
+    config = {CONF_BOARD: "my_custom_board", **yaml}
+    assert _resolve_board(config) is config
+
+
 def test_yaml_toolchain_key_resolves() -> None:
     """The documented `toolchain: arduino` YAML key selects the native path."""
     CORE.toolchain = None