diff --git a/cmd/gateway/main.go b/cmd/gateway/main.go
index 3f37124..4dfb56e 100644
--- a/cmd/gateway/main.go
+++ b/cmd/gateway/main.go
@@ -1,7 +1,9 @@
 package main
 
 import (
+	"database/sql"
 	"flag"
+	"fmt"
 	"log"
 	"net/http"
 	"os"
@@ -49,7 +51,7 @@ func main() {
 	}
 
 	// Initialize conversation store (1 hour TTL)
-	convStore := conversation.NewStore(1 * time.Hour)
+	convStore := conversation.NewMemoryStore(1 * time.Hour)
 	logger.Printf("Conversation store initialized (TTL: 1h)")
 
 	gatewayServer := server.New(registry, convStore, logger)
@@ -78,6 +80,38 @@ func main() {
 	}
 }
 
+func initConversationStore(cfg config.ConversationConfig, logger *log.Logger) (conversation.Store, error) {
+	var ttl time.Duration
+	if cfg.TTL != "" {
+		parsed, err := time.ParseDuration(cfg.TTL)
+		if err != nil {
+			return nil, fmt.Errorf("invalid conversation ttl %q: %w", cfg.TTL, err)
+		}
+		ttl = parsed
+	}
+
+	switch cfg.Store {
+	case "sql":
+		driver := cfg.Driver
+		if driver == "" {
+			driver = "sqlite3"
+		}
+		db, err := sql.Open(driver, cfg.DSN)
+		if err != nil {
+			return nil, fmt.Errorf("open database: %w", err)
+		}
+		store, err := conversation.NewSQLStore(db, driver, ttl)
+		if err != nil {
+			return nil, fmt.Errorf("init sql store: %w", err)
+		}
+		logger.Printf("Conversation store initialized (sql/%s, TTL: %s)", driver, ttl)
+		return store, nil
+	default:
+		logger.Printf("Conversation store initialized (memory, TTL: %s)", ttl)
+		return conversation.NewMemoryStore(ttl), nil
+	}
+}
+
 func loggingMiddleware(next http.Handler, logger *log.Logger) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		start := time.Now()
diff --git a/internal/conversation/conversation.go b/internal/conversation/conversation.go
index d65be22..2013517 100644
--- a/internal/conversation/conversation.go
+++ b/internal/conversation/conversation.go
@@ -7,8 +7,17 @@ import (
 	"github.com/yourusername/go-llm-gateway/internal/api"
 )
 
-// Store manages conversation history with automatic expiration.
-type Store struct {
+// Store defines the interface for conversation storage backends.
+type Store interface {
+	Get(id string) (*Conversation, bool)
+	Create(id string, model string, messages []api.Message) *Conversation
+	Append(id string, messages ...api.Message) (*Conversation, bool)
+	Delete(id string)
+	Size() int
+}
+
+// MemoryStore manages conversation history in-memory with automatic expiration.
+type MemoryStore struct {
 	conversations map[string]*Conversation
 	mu            sync.RWMutex
 	ttl           time.Duration
@@ -23,21 +32,23 @@ type Conversation struct {
 	UpdatedAt time.Time
 }
 
-// NewStore creates a conversation store with the given TTL.
-func NewStore(ttl time.Duration) *Store {
-	s := &Store{
+// NewMemoryStore creates an in-memory conversation store with the given TTL.
+func NewMemoryStore(ttl time.Duration) *MemoryStore {
+	s := &MemoryStore{
 		conversations: make(map[string]*Conversation),
 		ttl:           ttl,
 	}
 	
-	// Start cleanup goroutine
-	go s.cleanup()
+	// Start cleanup goroutine if TTL is set
+	if ttl > 0 {
+		go s.cleanup()
+	}
 	
 	return s
 }
 
 // Get retrieves a conversation by ID.
-func (s *Store) Get(id string) (*Conversation, bool) {
+func (s *MemoryStore) Get(id string) (*Conversation, bool) {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 	
@@ -46,7 +57,7 @@ func (s *Store) Get(id string) (*Conversation, bool) {
 }
 
 // Create creates a new conversation with the given messages.
-func (s *Store) Create(id string, model string, messages []api.Message) *Conversation {
+func (s *MemoryStore) Create(id string, model string, messages []api.Message) *Conversation {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	
@@ -64,7 +75,7 @@ func (s *Store) Create(id string, model string, messages []api.Message) *Convers
 }
 
 // Append adds new messages to an existing conversation.
-func (s *Store) Append(id string, messages ...api.Message) (*Conversation, bool) {
+func (s *MemoryStore) Append(id string, messages ...api.Message) (*Conversation, bool) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	
@@ -80,7 +91,7 @@ func (s *Store) Append(id string, messages ...api.Message) (*Conversation, bool)
 }
 
 // Delete removes a conversation from the store.
-func (s *Store) Delete(id string) {
+func (s *MemoryStore) Delete(id string) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	
@@ -88,7 +99,7 @@ func (s *Store) Delete(id string) {
 }
 
 // cleanup periodically removes expired conversations.
-func (s *Store) cleanup() {
+func (s *MemoryStore) cleanup() {
 	ticker := time.NewTicker(1 * time.Minute)
 	defer ticker.Stop()
 	
@@ -105,7 +116,7 @@ func (s *Store) cleanup() {
 }
 
 // Size returns the number of active conversations.
-func (s *Store) Size() int {
+func (s *MemoryStore) Size() int {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 	return len(s.conversations)
diff --git a/internal/conversation/sql_store.go b/internal/conversation/sql_store.go
new file mode 100644
index 0000000..3080bc7
--- /dev/null
+++ b/internal/conversation/sql_store.go
@@ -0,0 +1,133 @@
+package conversation
+
+import (
+	"database/sql"
+	"encoding/json"
+	"time"
+
+	"github.com/yourusername/go-llm-gateway/internal/api"
+)
+
+// sqlDialect holds driver-specific SQL statements.
+type sqlDialect struct {
+	getByID    string
+	upsert     string
+	update     string
+	deleteByID string
+	cleanup    string
+}
+
+func newDialect(driver string) sqlDialect {
+	if driver == "pgx" || driver == "postgres" {
+		return sqlDialect{
+			getByID:    `SELECT id, model, messages, created_at, updated_at FROM conversations WHERE id = $1`,
+			upsert:     `INSERT INTO conversations (id, model, messages, created_at, updated_at) VALUES ($1, $2, $3, $4, $5) ON CONFLICT (id) DO UPDATE SET model = EXCLUDED.model, messages = EXCLUDED.messages, updated_at = EXCLUDED.updated_at`,
+			update:     `UPDATE conversations SET messages = $1, updated_at = $2 WHERE id = $3`,
+			deleteByID: `DELETE FROM conversations WHERE id = $1`,
+			cleanup:    `DELETE FROM conversations WHERE updated_at < $1`,
+		}
+	}
+	return sqlDialect{
+		getByID:    `SELECT id, model, messages, created_at, updated_at FROM conversations WHERE id = ?`,
+		upsert:     `REPLACE INTO conversations (id, model, messages, created_at, updated_at) VALUES (?, ?, ?, ?, ?)`,
+		update:     `UPDATE conversations SET messages = ?, updated_at = ? WHERE id = ?`,
+		deleteByID: `DELETE FROM conversations WHERE id = ?`,
+		cleanup:    `DELETE FROM conversations WHERE updated_at < ?`,
+	}
+}
+
+// SQLStore manages conversation history in a SQL database with automatic expiration.
+type SQLStore struct {
+	db      *sql.DB
+	ttl     time.Duration
+	dialect sqlDialect
+}
+
+// NewSQLStore creates a SQL-backed conversation store. It creates the
+// conversations table if it does not already exist and starts a background
+// goroutine to remove expired rows.
+func NewSQLStore(db *sql.DB, driver string, ttl time.Duration) (*SQLStore, error) {
+	_, err := db.Exec(`CREATE TABLE IF NOT EXISTS conversations (
+		id         TEXT PRIMARY KEY,
+		model      TEXT NOT NULL,
+		messages   TEXT NOT NULL,
+		created_at TIMESTAMP NOT NULL,
+		updated_at TIMESTAMP NOT NULL
+	)`)
+	if err != nil {
+		return nil, err
+	}
+
+	s := &SQLStore{db: db, ttl: ttl, dialect: newDialect(driver)}
+	if ttl > 0 {
+		go s.cleanup()
+	}
+	return s, nil
+}
+
+func (s *SQLStore) Get(id string) (*Conversation, bool) {
+	row := s.db.QueryRow(s.dialect.getByID, id)
+
+	var conv Conversation
+	var msgJSON string
+	err := row.Scan(&conv.ID, &conv.Model, &msgJSON, &conv.CreatedAt, &conv.UpdatedAt)
+	if err != nil {
+		return nil, false
+	}
+
+	if err := json.Unmarshal([]byte(msgJSON), &conv.Messages); err != nil {
+		return nil, false
+	}
+
+	return &conv, true
+}
+
+func (s *SQLStore) Create(id string, model string, messages []api.Message) *Conversation {
+	now := time.Now()
+	msgJSON, _ := json.Marshal(messages)
+
+	_, _ = s.db.Exec(s.dialect.upsert, id, model, string(msgJSON), now, now)
+
+	return &Conversation{
+		ID:        id,
+		Messages:  messages,
+		Model:     model,
+		CreatedAt: now,
+		UpdatedAt: now,
+	}
+}
+
+func (s *SQLStore) Append(id string, messages ...api.Message) (*Conversation, bool) {
+	conv, ok := s.Get(id)
+	if !ok {
+		return nil, false
+	}
+
+	conv.Messages = append(conv.Messages, messages...)
+	conv.UpdatedAt = time.Now()
+
+	msgJSON, _ := json.Marshal(conv.Messages)
+	_, _ = s.db.Exec(s.dialect.update, string(msgJSON), conv.UpdatedAt, id)
+
+	return conv, true
+}
+
+func (s *SQLStore) Delete(id string) {
+	_, _ = s.db.Exec(s.dialect.deleteByID, id)
+}
+
+func (s *SQLStore) Size() int {
+	var count int
+	_ = s.db.QueryRow(`SELECT COUNT(*) FROM conversations`).Scan(&count)
+	return count
+}
+
+func (s *SQLStore) cleanup() {
+	ticker := time.NewTicker(1 * time.Minute)
+	defer ticker.Stop()
+
+	for range ticker.C {
+		cutoff := time.Now().Add(-s.ttl)
+		_, _ = s.db.Exec(s.dialect.cleanup, cutoff)
+	}
+}
diff --git a/internal/server/server.go b/internal/server/server.go
index aada7d0..b846415 100644
--- a/internal/server/server.go
+++ b/internal/server/server.go
@@ -14,12 +14,12 @@ import (
 // GatewayServer hosts the Open Responses API for the gateway.
 type GatewayServer struct {
 	registry *providers.Registry
-	convs    *conversation.Store
+	convs    conversation.Store
 	logger   *log.Logger
 }
 
 // New creates a GatewayServer bound to the provider registry.
-func New(registry *providers.Registry, convs *conversation.Store, logger *log.Logger) *GatewayServer {
+func New(registry *providers.Registry, convs conversation.Store, logger *log.Logger) *GatewayServer {
 	return &GatewayServer{
 		registry: registry,
 		convs:    convs,