diff --git a/wfe-yaml/src/lib.rs b/wfe-yaml/src/lib.rs
index 7f39ba2..a0c2777 100644
--- a/wfe-yaml/src/lib.rs
+++ b/wfe-yaml/src/lib.rs
@@ -6,13 +6,24 @@ pub mod schema;
 pub mod types;
 pub mod validation;
 
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
+use std::path::Path;
 
 use serde::de::Error as _;
+use serde::Deserialize;
 
 use crate::compiler::CompiledWorkflow;
 use crate::error::YamlWorkflowError;
 
+/// Top-level YAML file with optional includes.
+#[derive(Deserialize)]
+pub struct YamlWorkflowFileWithIncludes {
+    #[serde(default)]
+    pub include: Vec<String>,
+    #[serde(flatten)]
+    pub file: schema::YamlWorkflowFile,
+}
+
 /// Load workflows from a YAML file path, applying variable interpolation.
 /// Returns a Vec of compiled workflows (supports multi-workflow files).
 pub fn load_workflow(
@@ -76,6 +87,116 @@ pub fn load_single_workflow_from_str(
     Ok(workflows.remove(0))
 }
 
+/// Load workflows from a YAML string, resolving `include:` paths relative to `base_path`.
+///
+/// Processing:
+/// 1. Parse the main YAML to get `include:` paths.
+/// 2. For each include path, load and parse that YAML file.
+/// 3. Merge workflow specs from included files into the main file's specs.
+/// 4. Main file's workflows take precedence over included ones (by ID).
+/// 5. Proceed with normal validation + compilation.
+pub fn load_workflow_with_includes(
+    yaml: &str,
+    base_path: &Path,
+    config: &HashMap<String, serde_json::Value>,
+) -> Result<Vec<CompiledWorkflow>, YamlWorkflowError> {
+    let mut visited = HashSet::new();
+    let canonical = base_path
+        .canonicalize()
+        .unwrap_or_else(|_| base_path.to_path_buf());
+    visited.insert(canonical.to_string_lossy().to_string());
+
+    let interpolated = interpolation::interpolate(yaml, config)?;
+    let raw_value: serde_yaml::Value = serde_yaml::from_str(&interpolated)?;
+    let merged_value = yaml_merge_keys::merge_keys_serde(raw_value)
+        .map_err(|e| {
+            YamlWorkflowError::Parse(serde_yaml::Error::custom(format!(
+                "merge key resolution failed: {e}"
+            )))
+        })?;
+
+    let with_includes: YamlWorkflowFileWithIncludes = serde_yaml::from_value(merged_value)?;
+
+    let mut main_specs = resolve_workflow_specs(with_includes.file)?;
+
+    // Process includes.
+    for include_path_str in &with_includes.include {
+        let include_path = base_path.parent().unwrap_or(base_path).join(include_path_str);
+        load_includes_recursive(
+            &include_path,
+            config,
+            &mut main_specs,
+            &mut visited,
+        )?;
+    }
+
+    // Main file takes precedence: included specs are only added if their ID
+    // isn't already present. This is handled by load_includes_recursive.
+
+    validation::validate_multi(&main_specs)?;
+
+    let mut results = Vec::with_capacity(main_specs.len());
+    for spec in &main_specs {
+        results.push(compiler::compile(spec)?);
+    }
+
+    Ok(results)
+}
+
+fn load_includes_recursive(
+    path: &Path,
+    config: &HashMap<String, serde_json::Value>,
+    specs: &mut Vec<schema::WorkflowSpec>,
+    visited: &mut HashSet<String>,
+) -> Result<(), YamlWorkflowError> {
+    let canonical = path
+        .canonicalize()
+        .map_err(|e| {
+            YamlWorkflowError::Io(std::io::Error::new(
+                std::io::ErrorKind::NotFound,
+                format!("Include file not found: {}: {e}", path.display()),
+            ))
+        })?;
+
+    let canonical_str = canonical.to_string_lossy().to_string();
+    if !visited.insert(canonical_str.clone()) {
+        return Err(YamlWorkflowError::Validation(format!(
+            "Circular include detected: '{}'",
+            path.display()
+        )));
+    }
+
+    let yaml = std::fs::read_to_string(&canonical)?;
+    let interpolated = interpolation::interpolate(&yaml, config)?;
+    let raw_value: serde_yaml::Value = serde_yaml::from_str(&interpolated)?;
+    let merged_value = yaml_merge_keys::merge_keys_serde(raw_value)
+        .map_err(|e| {
+            YamlWorkflowError::Parse(serde_yaml::Error::custom(format!(
+                "merge key resolution failed: {e}"
+            )))
+        })?;
+
+    let with_includes: YamlWorkflowFileWithIncludes = serde_yaml::from_value(merged_value)?;
+
+    let included_specs = resolve_workflow_specs(with_includes.file)?;
+
+    // Existing IDs in main specs take precedence.
+    let existing_ids: HashSet<String> = specs.iter().map(|s| s.id.clone()).collect();
+    for spec in included_specs {
+        if !existing_ids.contains(&spec.id) {
+            specs.push(spec);
+        }
+    }
+
+    // Recurse into nested includes.
+    for nested_include in &with_includes.include {
+        let nested_path = canonical.parent().unwrap_or(&canonical).join(nested_include);
+        load_includes_recursive(&nested_path, config, specs, visited)?;
+    }
+
+    Ok(())
+}
+
 /// Resolve a YamlWorkflowFile into a list of WorkflowSpecs.
 fn resolve_workflow_specs(
     file: schema::YamlWorkflowFile,