diff --git a/adapters.go b/adapters.go
index 4a28b0b..368b5ef 100644
--- a/adapters.go
+++ b/adapters.go
@@ -1,16 +1,20 @@
 package conf
 
 import (
+	"bytes"
 	"encoding/json"
 	"errors"
 	"fmt"
+	"reflect"
 	"strings"
+	"unicode"
 
 	"github.com/hashicorp/hcl/v2"
 	"github.com/hashicorp/hcl/v2/gohcl"
 	"github.com/hashicorp/hcl/v2/hclsimple"
 	"github.com/hashicorp/hcl/v2/hclwrite"
 	"github.com/pelletier/go-toml/v2"
+	"gopkg.in/ini.v1"
 	"gopkg.in/yaml.v3"
 )
 
@@ -26,6 +30,7 @@ const (
 	typeTOML
 	typeHCL
 	typeYAML
+	typeINI
 )
 
 // getType returns the type of the config file.
@@ -40,6 +45,9 @@ func getType(filename string) filetype {
 	case strings.HasSuffix(filename, ".yml") ||
 		strings.HasSuffix(filename, ".yaml"):
 		return typeYAML
+	case strings.HasSuffix(filename, ".ini") ||
+		strings.HasSuffix(filename, ".cfg"):
+		return typeINI
 	default:
 		return typeInvalid
 	}
@@ -58,6 +66,8 @@ func unmarshal(filepath string, data []byte, v any) error {
 		return unmarshalHCL(filepath, data, v)
 	case typeYAML:
 		return unmarshalYAML(data, v)
+	case typeINI:
+		return unmarshalINI(data, v)
 	default:
 		return ErrUnsupportedFileType
 	}
@@ -74,6 +84,8 @@ func marshal(ft filetype, v any) ([]byte, error) {
 		return marshalHCL(v)
 	case typeYAML:
 		return marshalYAML(v)
+	case typeINI:
+		return marshalINI(v)
 	default:
 		return nil, ErrUnsupportedFileType
 	}
@@ -178,3 +190,55 @@ func marshalYAML(v any) ([]byte, error) {
 
 	return data, nil
 }
+
+// unmarshalINI unmarshals the given data to the given struct.
+func unmarshalINI(data []byte, v any) error {
+	opts := ini.LoadOptions{}
+	cfg, err := ini.LoadSources(opts, data)
+	if err != nil {
+		return parseError(err)
+	}
+
+	cfg.NameMapper = iniNameMapper
+
+	err = cfg.MapTo(v)
+	if err != nil {
+		return parseError(err)
+	}
+
+	return nil
+}
+
+// marshalYAML marshals the given struct to bytes.
+func marshalINI(v any) ([]byte, error) {
+	cfg := ini.Empty()
+
+	val := reflect.ValueOf(v)
+	if val.Kind() != reflect.Ptr {
+		v = &v
+	}
+
+	err := ini.ReflectFromWithMapper(cfg, v, iniNameMapper)
+	if err != nil {
+		return nil, fmt.Errorf("cannot generate config content: %w", err)
+	}
+
+	var buf bytes.Buffer
+	cfg.WriteTo(&buf)
+	data := buf.Bytes()
+
+	return data, nil
+}
+
+func iniNameMapper(raw string) string {
+	newstr := make([]rune, 0, len(raw))
+	for i, chr := range raw {
+		if isUpper := 'A' <= chr && chr <= 'Z'; isUpper {
+			if i > 0 {
+				newstr = append(newstr, '_')
+			}
+		}
+		newstr = append(newstr, unicode.ToLower(chr))
+	}
+	return string(newstr)
+}
diff --git a/config_test.go b/config_test.go
index d302d3b..9e55316 100644
--- a/config_test.go
+++ b/config_test.go
@@ -35,6 +35,12 @@ func TestYAMLFiles(t *testing.T) {
 	runTestSuite(t, "yaml")
 }
 
+func TestINIFiles(t *testing.T) {
+	t.Parallel()
+
+	runTestSuite(t, "ini")
+}
+
 func TestUnknownFiles(t *testing.T) {
 	t.Parallel()
 
diff --git a/go.mod b/go.mod
index 6eeb6a3..31ee2dd 100644
--- a/go.mod
+++ b/go.mod
@@ -2,11 +2,12 @@ module code.bcarlin.net/go/conf
 
 go 1.22
 
-toolchain go1.23.4
-
 require (
+	github.com/hashicorp/hcl/v2 v2.23.0
 	github.com/pelletier/go-toml/v2 v2.2.3
 	github.com/stretchr/testify v1.10.0
+	gopkg.in/ini.v1 v1.67.0
+	gopkg.in/yaml.v3 v3.0.1
 )
 
 require (
@@ -15,7 +16,6 @@ require (
 	github.com/apparentlymart/go-textseg/v15 v15.0.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/google/go-cmp v0.6.0 // indirect
-	github.com/hashicorp/hcl/v2 v2.23.0 // indirect
 	github.com/mitchellh/go-wordwrap v0.0.0-20150314170334-ad45545899c7 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/zclconf/go-cty v1.13.0 // indirect
@@ -23,5 +23,4 @@ require (
 	golang.org/x/sys v0.5.0 // indirect
 	golang.org/x/text v0.11.0 // indirect
 	golang.org/x/tools v0.6.0 // indirect
-	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
diff --git a/go.sum b/go.sum
index b356020..45fb1af 100644
--- a/go.sum
+++ b/go.sum
@@ -6,6 +6,8 @@ github.com/apparentlymart/go-textseg/v15 v15.0.0 h1:uYvfpb3DyLSCGWnctWKGj857c6ew
 github.com/apparentlymart/go-textseg/v15 v15.0.0/go.mod h1:K8XmNZdhEBkdlyDdvbmmsvpAG721bKi0joRfFdHIWJ4=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/go-test/deep v1.0.3 h1:ZrJSEWsXzPOxaZnFteGEfooLba+ju3FYIbOrS+rQd68=
+github.com/go-test/deep v1.0.3/go.mod h1:wGDj63lr65AM2AQyKZd/NYHGb0R+1RLqB8NKt3aSFNA=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/hashicorp/hcl/v2 v2.23.0 h1:Fphj1/gCylPxHutVSEOf2fBOh1VE4AuLV7+kbJf3qos=
@@ -20,8 +22,12 @@ github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOf
 github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 github.com/zclconf/go-cty v1.13.0 h1:It5dfKTTZHe9aeppbNOda3mN7Ag7sg6QkBNm6TkyFa0=
 github.com/zclconf/go-cty v1.13.0/go.mod h1:YKQzy/7pZ7iq2jNFzy5go57xdxdWoLLpaEp4u238AE0=
+github.com/zclconf/go-cty-debug v0.0.0-20240509010212-0d6042c53940 h1:4r45xpDWB6ZMSMNJFMOjqrGHynW3DIBuR2H9j0ug+Mo=
+github.com/zclconf/go-cty-debug v0.0.0-20240509010212-0d6042c53940/go.mod h1:CmBdvvj3nqzfzJ6nTCIwDTPZ56aVGvDrmztiO5g3qrM=
 golang.org/x/mod v0.8.0 h1:LUYupSeNrTNCGzR/hVBk2NHZO4hXcVaW1k4Qx7rjPx8=
 golang.org/x/mod v0.8.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
+golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
+golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.5.0 h1:MUK/U/4lj1t1oPg0HfuXDN/Z1wv31ZJ/YcPiGccS4DU=
 golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/text v0.11.0 h1:LAntKIrcmeSKERyiOh0XMV39LXS8IE9UL2yP7+f5ij4=
@@ -30,5 +36,7 @@ golang.org/x/tools v0.6.0 h1:BOw41kyTf3PuCW1pVQf8+Cyg8pMlkYB1oo9iJ6D/lKM=
 golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/ini.v1 v1.67.0 h1:Dgnx+6+nfE+IfzjUEISNeydPJh9AXNNsWbGP9KzCsOA=
+gopkg.in/ini.v1 v1.67.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/test_data/full.ini b/test_data/full.ini
new file mode 100644
index 0000000..91197e4
--- /dev/null
+++ b/test_data/full.ini
@@ -0,0 +1,3 @@
+string    = default string
+invariant = should not change
+int       = 1
diff --git a/test_data/invalid.ini b/test_data/invalid.ini
new file mode 100644
index 0000000..ce94f17
--- /dev/null
+++ b/test_data/invalid.ini
@@ -0,0 +1 @@
+String not ini
diff --git a/test_data/part1.ini b/test_data/part1.ini
new file mode 100644
index 0000000..0f0d3b9
--- /dev/null
+++ b/test_data/part1.ini
@@ -0,0 +1 @@
+string = foo
diff --git a/test_data/part2.ini b/test_data/part2.ini
new file mode 100644
index 0000000..f09a38c
--- /dev/null
+++ b/test_data/part2.ini
@@ -0,0 +1 @@
+int = 42
diff --git a/test_data/same1.ini b/test_data/same1.ini
new file mode 100644
index 0000000..0f0d3b9
--- /dev/null
+++ b/test_data/same1.ini
@@ -0,0 +1 @@
+string = foo
diff --git a/test_data/same2.ini b/test_data/same2.ini
new file mode 100644
index 0000000..07e0ced
--- /dev/null
+++ b/test_data/same2.ini
@@ -0,0 +1 @@
+string = bar
diff --git a/test_data/unknown.ini b/test_data/unknown.ini
new file mode 100644
index 0000000..5b2dcf1
--- /dev/null
+++ b/test_data/unknown.ini
@@ -0,0 +1,3 @@
+string = config string
+int = 42
+unknown = foo
diff --git a/test_data/valid.ini b/test_data/valid.ini
new file mode 100644
index 0000000..4e6f923
--- /dev/null
+++ b/test_data/valid.ini
@@ -0,0 +1,2 @@
+string = config string
+int = 42