diff --git a/AGENTS.md b/AGENTS.md
index 57321bf..c92fc47 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -138,10 +138,12 @@ Show the active configuration (after all overrides applied):
 | `NODE_LOOKUP_URL` | `puppetdb_url` | PuppetDB facts endpoint |
 | `NODE_LOOKUP_ROLE_FACT` | `role_fact` | Fact name used by `-R` flag |
 | `NODE_LOOKUP_PUPPETBOARD_URL` | `puppetboard_url` | Puppetboard base URL (pburl / pblastreport) |
+| `NODE_LOOKUP_DOMAIN` | `domain` | Domain appended to short (dotless) `-n` node names (default `main.unkin.net`) |
 
-### CLI flag
+### CLI flags
 
 `--url <url>` overrides the PuppetDB URL for a single invocation (highest precedence).
+`--domain <domain>` overrides the auto-qualify domain for a single invocation.
 
 ## Code Patterns
 
@@ -152,6 +154,7 @@ Show the active configuration (after all overrides applied):
 - **`queryPuppetDB(url, query)`**: takes the URL as a parameter — never reads globals.
 - **`processResults()`**: iterates facts, returns sorted `"certname value"` strings. JSON string values are unquoted; other JSON types rendered as compact JSON.
 - **Output modes**: JSON (`-j`), count (`-C`), Ansible YAML (`-A`), node-only (`-1`), value-only (`-2`), default (node + value). `-j` and `-A` share `factsByHost()`, so both attach the queried fact(s) per host — as an object under the host (`-j`) or as inventory host vars (`-A`).
+- **Short node names / `qualifyNode()`**: a `-n` value (and stdin-sourced node names) with no dot is auto-qualified to `<name>.<domain>` (domain defaults to `main.unkin.net`, overridable via `--domain`/`NODE_LOOKUP_DOMAIN`), so `-n ausyd1nxvm2120` resolves the same as its FQDN. A name that already contains a dot (any domain) is left unchanged; a single trailing dot is stripped; empty input is preserved.
 - **Stdin support**: `stdinReader()` reads node names from stdin only when it is a real pipe/redirect carrying data (and no `-n` given). Terminals, `/dev/null`, and empty/closed pipes fall through to a normal query — so running without a TTY (e.g. invoked by an agent or CI) behaves like an interactive run instead of consuming empty input.
 - **SIGPIPE handling**: `signal.Ignore(syscall.SIGPIPE)` so pipes to `head` etc. work cleanly.
 
diff --git a/main.go b/main.go
index 63e9e90..2b22e86 100644
--- a/main.go
+++ b/main.go
@@ -22,6 +22,7 @@ const (
 	defaultPuppetDBURL    = "http://puppetdbapi.service.consul:8080/pdb/query/v4/facts"
 	defaultRoleFact       = "enc_role"
 	defaultPuppetboardURL = "https://puppetboard.k8s.syd1.au.unkin.net"
+	defaultDomain         = "main.unkin.net"
 	configFileName        = "config.yaml"
 	appName               = "node-lookup"
 )
@@ -37,6 +38,8 @@ type config struct {
 	// the shared config file also configures the companion tools (pburl,
 	// pblastreport) that read this same file.
 	PuppetboardURL string `yaml:"puppetboard_url"`
+	// Domain is appended to a short (dotless) -n node name to form its FQDN.
+	Domain string `yaml:"domain"`
 }
 
 func defaultConfig() config {
@@ -44,6 +47,7 @@ func defaultConfig() config {
 		PuppetDBURL:    defaultPuppetDBURL,
 		RoleFact:       defaultRoleFact,
 		PuppetboardURL: defaultPuppetboardURL,
+		Domain:         defaultDomain,
 	}
 }
 
@@ -87,6 +91,9 @@ func loadConfig() (config, error) {
 	if v := os.Getenv("NODE_LOOKUP_PUPPETBOARD_URL"); v != "" {
 		cfg.PuppetboardURL = v
 	}
+	if v := os.Getenv("NODE_LOOKUP_DOMAIN"); v != "" {
+		cfg.Domain = v
+	}
 
 	return cfg, nil
 }
@@ -105,7 +112,7 @@ func writeDefaultConfig() error {
 
 	cfg := defaultConfig()
 	data, _ := yaml.Marshal(cfg)
-	header := []byte("# node-lookup configuration\n# Fields can be overridden with env vars: NODE_LOOKUP_URL, NODE_LOOKUP_ROLE_FACT, NODE_LOOKUP_PUPPETBOARD_URL\n# puppetboard_url is used by the companion tools (pburl, pblastreport).\n\n")
+	header := []byte("# node-lookup configuration\n# Fields can be overridden with env vars: NODE_LOOKUP_URL, NODE_LOOKUP_ROLE_FACT, NODE_LOOKUP_PUPPETBOARD_URL, NODE_LOOKUP_DOMAIN\n# puppetboard_url is used by the companion tools (pburl, pblastreport).\n# domain is appended to short (dotless) -n node names to form their FQDN.\n\n")
 	if err := os.WriteFile(path, append(header, data...), 0o644); err != nil {
 		return fmt.Errorf("writing config: %w", err)
 	}
@@ -144,6 +151,21 @@ func nameFilter(names []string) []interface{} {
 	return or
 }
 
+// qualifyNode auto-qualifies a short (dotless) node name by appending
+// ".<domain>", so `-n ausyd1nxvm2120` resolves the same as its FQDN. A name
+// that already contains a dot is treated as already-qualified (including names
+// in other domains like *.k8s.syd1.au.unkin.net) and returned unchanged. A
+// single trailing dot is stripped first, so a dotless name with a trailing dot
+// is still qualified. Empty input is returned unchanged to preserve the
+// existing "no node given" behavior.
+func qualifyNode(name, domain string) string {
+	name = strings.TrimSuffix(name, ".")
+	if name == "" || strings.Contains(name, ".") {
+		return name
+	}
+	return name + "." + domain
+}
+
 func buildQuery(node, factName, match, roleFact string, showRole, partial, inverse bool) string {
 	type filter = []interface{}
 	var filters []filter
@@ -318,6 +340,8 @@ func allFactsForNode(puppetDBURL, node string) ([]fact, error) {
 func run(cfg config, nodeName, factName, match string, showRole, partial, inverse, nodeOnly, valueOnly, count, ansible, jsonMode, allFacts bool) error {
 	signal.Ignore(syscall.SIGPIPE)
 
+	nodeName = qualifyNode(nodeName, cfg.Domain)
+
 	if allFacts {
 		if nodeName == "" {
 			return fmt.Errorf("-a requires -n")
@@ -365,7 +389,7 @@ func run(cfg config, nodeName, factName, match string, showRole, partial, invers
 				if len(fields) == 0 {
 					continue
 				}
-				if err := doQuery(fields[0]); err != nil {
+				if err := doQuery(qualifyNode(fields[0], cfg.Domain)); err != nil {
 					fmt.Fprintln(os.Stderr, "error:", err)
 				}
 			}
@@ -446,6 +470,7 @@ func main() {
 		jsonMode    bool
 		allFacts    bool
 		puppetDBURL string
+		domain      string
 	)
 
 	rootCmd := &cobra.Command{
@@ -461,6 +486,9 @@ func main() {
 			if cmd.Flags().Changed("url") {
 				cfg.PuppetDBURL = puppetDBURL
 			}
+			if cmd.Flags().Changed("domain") {
+				cfg.Domain = domain
+			}
 			return nil
 		},
 		RunE: func(cmd *cobra.Command, args []string) error {
@@ -482,6 +510,7 @@ func main() {
 	f.BoolVarP(&ansible, "ansible", "A", false, "Output as Ansible inventory")
 	f.BoolVarP(&jsonMode, "json", "j", false, "Emit valid JSON for all output")
 	f.BoolVarP(&allFacts, "all", "a", false, "Show all facts for a node (requires -n)")
+	f.StringVar(&domain, "domain", cfg.Domain, "Domain appended to short (dotless) -n node names (overrides config and NODE_LOOKUP_DOMAIN)")
 	rootCmd.PersistentFlags().StringVar(&puppetDBURL, "url", cfg.PuppetDBURL, "PuppetDB facts URL (overrides config and NODE_LOOKUP_URL)")
 
 	configCmd := &cobra.Command{
@@ -506,6 +535,7 @@ func main() {
 			fmt.Printf("puppetdb_url   : %s\n", cfg.PuppetDBURL)
 			fmt.Printf("role_fact      : %s\n", cfg.RoleFact)
 			fmt.Printf("puppetboard_url: %s\n", cfg.PuppetboardURL)
+			fmt.Printf("domain         : %s\n", cfg.Domain)
 			return nil
 		},
 		SilenceUsage: true,
diff --git a/main_test.go b/main_test.go
index b36af7a..c65f7b5 100644
--- a/main_test.go
+++ b/main_test.go
@@ -167,6 +167,35 @@ func TestSplitFactNames(t *testing.T) {
 	}
 }
 
+func TestQualifyNode(t *testing.T) {
+	const domain = "main.unkin.net"
+	cases := []struct {
+		name string
+		in   string
+		want string
+	}{
+		{"short name appends domain", "ausyd1nxvm2120", "ausyd1nxvm2120.main.unkin.net"},
+		{"fqdn in default domain unchanged", "ausyd1nxvm2120.main.unkin.net", "ausyd1nxvm2120.main.unkin.net"},
+		{"multi-label fqdn other domain unchanged", "foo.k8s.syd1.au.unkin.net", "foo.k8s.syd1.au.unkin.net"},
+		{"short name with trailing dot qualified", "ausyd1nxvm2120.", "ausyd1nxvm2120.main.unkin.net"},
+		{"fqdn with trailing dot stripped", "foo.main.unkin.net.", "foo.main.unkin.net"},
+		{"empty unchanged", "", ""},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := qualifyNode(tc.in, domain); got != tc.want {
+				t.Fatalf("qualifyNode(%q, %q) = %q, want %q", tc.in, domain, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestQualifyNode_CustomDomain(t *testing.T) {
+	if got := qualifyNode("host1", "example.com"); got != "host1.example.com" {
+		t.Fatalf("qualifyNode with custom domain = %q, want host1.example.com", got)
+	}
+}
+
 func TestBuildQuery_SingleFact_NoOr(t *testing.T) {
 	q := buildQuery("", "ipaddress", "", "enc_role", false, false, false)
 	if strings.Contains(q, `"or"`) {
@@ -397,6 +426,22 @@ func TestLoadConfig_Defaults(t *testing.T) {
 	if cfg.RoleFact != defaultRoleFact {
 		t.Fatalf("expected default role fact, got %s", cfg.RoleFact)
 	}
+	if cfg.Domain != defaultDomain {
+		t.Fatalf("expected default domain, got %s", cfg.Domain)
+	}
+}
+
+func TestLoadConfig_DomainEnvOverride(t *testing.T) {
+	t.Setenv("XDG_CONFIG_HOME", t.TempDir())
+	t.Setenv("NODE_LOOKUP_DOMAIN", "example.com")
+
+	cfg, err := loadConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if cfg.Domain != "example.com" {
+		t.Fatalf("domain env override failed: %s", cfg.Domain)
+	}
 }
 
 func TestLoadConfig_EnvOverride(t *testing.T) {