diff --git a/error.go b/error.go
index 4645d41..42daca0 100644
--- a/error.go
+++ b/error.go
@@ -11,6 +11,7 @@ const INTERNAL_ERROR_MESSAGE = "internal error"
 //
 // Note: these are generic codes but map well to HTTP status codes.
 const (
+	EINVALID  = "invalid"
 	EINTERNAL = "internal"
 	ENOTFOUND = "not_found"
 )
diff --git a/user.go b/user.go
index 940704c..aa726f1 100644
--- a/user.go
+++ b/user.go
@@ -25,9 +25,49 @@ type User struct {
 	// Auths []*Auth `json:"auths"`
 }
 
+func (u *User) Validate() error {
+	if u.Name == "" {
+		return Errorf(EINVALID, "User name required.")
+	}
+	return nil
+}
+
 // UserService represents a service for managing users.
 type UserService interface {
 	// Retrieves a user by ID along with their associated auth objects
 	// Returns ENOTFOUND if user does not exist.
 	FindUserByID(ctx context.Context, id int) (*User, error)
+
+	// Retrieves a list of users by filter. Also returns total count of matching users
+	// which may differ from retruned results if filter.Limit is specified.
+	FindUsers(ctc context.Context, filter UserFilter) ([]*User, int, error)
+
+	// Creates a new use. This is only used for testing since users are typically
+	// cretaed during the OAuth creation process in the AuthService.CreateAuth().
+	CreateUser(ctx context.Context, user *User) error
+
+	// Updates a user object. Returns EUNAUTHORIZED if current user is not
+	// the user that is being updated. Returns ENOTFOUND if the user does not exist.
+	UpdateUser(ctx context.Context, id int, upd UserUpdate) (*User, error)
+
+	// Permanently deletes a user and all owned application resources. Returns EUNAUTHORIZED
+	// if current user is not the user being deleted. Returns ENOTFOUND if the user
+	// does not exist.
+	DeleteUser(ctx context.Context, id int) error
+}
+
+// UserFilter respresents a filter passed to FindUsers().
+type UserFilter struct {
+	ID     *int    `json:"id"`
+	Email  *string `json:"email"`
+	APIKey *string `json:"apiKey"`
+
+	// Restrict to subset of results
+	Offset int `json:"offset"`
+	Limit  int `json:"limit"`
+}
+
+type UserUpdate struct {
+	Name  *string `json:"name"`
+	Email *string `json:"email"`
 }
diff --git a/user_test.go b/user_test.go
new file mode 100644
index 0000000..f124f67
--- /dev/null
+++ b/user_test.go
@@ -0,0 +1,20 @@
+package ratchet
+
+import "testing"
+
+func TestUserValidation(t *testing.T) {
+	t.Run("user should return invalid", func(t *testing.T) {
+		u := &User{}
+		if ErrorCode(u.Validate()) != EINVALID {
+			t.Errorf("User validation should have failed but passed instead.")
+		}
+	})
+
+	t.Run("user validation should pass", func(t *testing.T) {
+		u := &User{Name: "Drew"}
+		if u.Validate() != nil {
+			t.Errorf("User validation failed")
+		}
+	})
+
+}