It is never too late to invest in mutual funds for retirement. As such, if you plan to invest in some of the best funds, the Zacks Mutual Fund Rank can provide you with valuable guidance.

The easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using the Zacks Mutual Fund Rank of over 19,000 mutual funds, we've identified three outstanding mutual funds that are ideally suited to help long-term investors pursue and achieve their retirement investing goals.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

If you are looking to diversify your portfolio, consider AB International Small Cap Adv (IRCYX). IRCYX is a Non US - Equity fund. Many of these funds like to allocate across emerging and developed markets, and will often focus on all cap levels. This fund is a winner, boasting an expense ratio of 1.07%, management fee of 1%, and a five-year annualized return track record of 10.52%.

Third Avenue Value Fund Investor (TVFVX). Expense ratio: 1.4%. Management fee: 0.9%. TVFVX is a Small Cap Value fund, and these funds are known for investing in companies with market caps under $2 billion. This fund has managed to produce a robust 23.34% over the last five years.

Cavanal Hill World Energy Institutional (AIWEX Quick QuoteAIWEX - Free Report) . Expense ratio: 0.9%. Management fee: 0.6%. Five year annual return: 28.46%. AIWEX is a Sector - Energy mutual fund, which encompasses a wide range of vastly changing and vitally important industries throughout this massive global sector.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.